1) Although the ordinary individual does not give selective attention enough consideration, its consequences may be felt in every waking minute. The system by which the human mind focuses its attention on a single subject for a period of time is known as selective attention (Banich & Compton, 2018). Human beings would be perpetually overwhelmed if they could not adapt to external conditions selectively. Additionally, they would struggle to execute the most fundamental tasks without abundant light, full stillness, and a clear, clean workplace. People can work efficiently and successfully in the face of innumerable factors of distraction and uncertainty if they pay attention selectively. One illustrative example of selective attention, where hearing is also involved, is when an individual decides to visit a restaurant with a friend. In this particular case, despite the presence and conversations in one room of a large number of strangers, a person is able to concentrate his attention on the speech of his interlocutor. An individuals hearing recognizes all the sound waves, but his brain can filter out unnecessary information to focus on one priority object, making a pleasant conversation possible. In contrast, reflexive attention occurs when a phenomenon provokes a reflex reaction of a person, causing an internal trigger. For instance, during a persons sleep, his alarm clock starts ringing, making a loud sound and emitting a screen light. Respectively, the persons attention is focused exclusively on the alarm clock, which must be turned off. To my mind, reflexive attention is more important since it is responsible for the basic reflexes of the human body. If this reaction is not functioning, a person will not perform the most basic actions and will endanger his life.
2) Automatic movements and processes are a logical continuation of similar actions performed in a mechanical manner. Stimuli or circumstances are connected to activities, routines, or processing algorithms, and then sets of these routines are related to one another, resulting in the occurrence of an automatic process (Banich & Compton, 2018). In this case, a single stimulus causes a relatively automatic string of activities. Controlled processing necessitates that individuals pay attention and make a conscious effort. Controlled processing occurs when a person is consciously aware of what he or she is doing. To put it differently, individuals are obliged to think about what is going on, solve issues, identify potential risks, and make decisions. Automatic processing eliminates the need for humans to consciously exert effort to regulate activities since it does not require them to pay attention. Automatic processing is performed without people giving it any consideration. When a person practices anything for a long time, the activity becomes part of the routine. When it comes to cycling, the first step to mastering this skill is maintaining balance at low speed. The next level will be performing basic maneuvers such as turns, U-turns, and obstacle avoidance. Ultimately, having mastered the initial skills, a person will feel confident, and with each new time, the automation of the cycling process will increase. When the operation becomes regular, an experienced bike rider may be able to perform various bike-riding duties (changing the gears of the bike) without thinking about it. Years of training have made it feasible to stop, respond to automobiles on the road, and alter speeds. In this situation, a skilled rider can do actions without being aware of them.
Reference
Banich, M. T., & Compton, R. J. (2018). Cognitive Neuroscience. Cambridge University Press.
The chemical properties of substances constitute an immediate element of the everyday life of people. One might observe the processes that represent chemical laws or principles in basic actions, procedures, or processes either observed or conducted. One of the examples of how chemistry is evident in everyday life might be the observation of gas laws. Indeed, it is known that temperature, pressure, and volume are the factors that influence the state of the gas. Thus, one might observe that a balloon filled with air shrinks when exposed to low temperatures. Such a change might be explained by the difference in the volume that the molecules of gas take under different temperatures. Another example of gas laws is the steam that appears when water boils, which indicates that this liquid evaporates and becomes gas. On the contrary, when the temperature lowers, the steam condenses and becomes liquid again.
Posting 2: Solution Solubility
Another concept from chemistry that one might observe in everyday life is solution solubility. This concept implies the tendency of mixed substances to dissolve into one solution. One might witness such processes in everyday life by observing how sugar melts in a hot cup of tea. It takes several seconds for the granules of sugar to dissolve in hot water. However, when placed in cold water, the sugar does not dissolve as quickly; it takes much longer for it to form a solution with water. To provide a different example, one might refer to another cooking process, which is making cocoa. Indeed, when putting cocoa powder into hot milk, the cocoa does not completely dissolve but mixes with milk. With time, it forms a layer of sediment, which shows that milk does not fully dissolve cocoa powder.
Serial Interviews: When and Why to Talk to Someone More Than Once
The article Serial Interviews: When and Why to Talk to Someone More Than Once by Benjamin Read was published in 2018 in the International Journal of Qualitative Methods. The paper is devoted to the description of the method of serial interviewing and the factors which determine its need in sociological research. This approach is most relevant in a number of cases when a single interview cannot provide sufficient information. In particular, this technique is more suitable when exploring difficult or poorly understood areas. Additionally, its application is appropriate when interviews are subject to time constraints, when exploring change or variation over time (Read 1). Moreover, serial interviews are an effective method of verifying information and data obtained.
This article provides detailed information on the serial interview method, which is an effective complement to other approaches. First of all, the paper was chosen because it contains examples of such an interview, as well as a review of the literature on the topic. Additionally, the cases when the use of this technique is preferable and the main differences from a single-session interview are considered in detail. The article provides comprehensive information about this technique since, in the literature, it is not always possible to find enough data on the practical application of serial interviewing.
The strengths of the article include describing the technique through an interesting case study. Moreover, the paper is well structured and allows the most complete assimilation of the information received. The weaknesses of the article include the fact that the author does not provide guidelines or advice on how to conduct a serial interview and develop questions. However, in general, the article is a full-fledged theoretical review of the method. This paper is recommended reading for all researchers who strive to expand the set of tools for knowledge and a complete understanding of existing research problems.
Interviewing Elites: Methodological Issues Confronting a Novice
The article Interviewing Elites: Methodological Issues Confronting a Novice by Xu Liu was published in 2018 in the International Journal of Qualitative Methods. This paper is devoted to the study of the problems of the process of interviewing respondents with a higher social status. In particular, attention is paid to making preparation, gaining access, establishing trust, and facing interpersonal challenges during interviews (Liu 1). The research is based on a survey of high-ranking officials of private educational institutions in China and presents their authoritative view of the problem.
The article was selected because it covers a common but insufficiently studied topic. It is often difficult for newcomers to sociological research to adapt to different types of respondents, which can lead to unsatisfactory results. Moreover, at the beginning of the paper, a detailed description of the concept of the elite is provided, which determines the factors which need to be paid attention to. This article contains information that is useful for deepening your knowledge of the interviewing method for a wider variety of groups.
The strengths of the article include a clear structure, which offers a detailed consideration of the methodology for conducting this type of interview. Moreover, the research is based on an assessment of the views of potential participants, which makes this information relevant and authoritative. In addition to the fact that a significant part of the paper is devoted to describing the strategy, the author also identifies possible obstacles for which one should prepare. This study does not contain weaknesses, as it provides complete theoretical and practical information on the entire process of interviewing respondents with high social status. This article is recommended for researchers seeking to expand their knowledge of the intervention of various social groups.
Works Cited
Liu, Xu. Interviewing Elites: Methodological Issues Confronting a Novice. International Journal of Qualitative Methods, vol. 17, no. 1, 2018, pp. 1-9. Web.
Read, Benjamin. Serial Interviews: When and Why to Talk to Someone More Than Once. International Journal of Qualitative Methods, vol. 17, no. 1, 2018, pp. 1-10. Web.
Fossils from the Late Devonian period, supposedly more than 360 million years old, were found in rocks in East Greenland. The fossils of this ancient animal made it clear that it had a generally developed system of fingers and limbs, so the species was quickly classified as a tetrapod. Ichthyostega was the first vertebrate animal found to have four limbs. However, it is now clear that it is challenging to call Ichthyostega a true tetrapod because of the primitiveness of the postcranial skeleton system, especially in comparison to modern quadrupedal animals. In addition, modern biology tends to believe that true tetrapods first appeared as a result of evolution only in the Triassic period, and thus Ichthyostega cannot be regarded as an official quadrupedal animal. Nevertheless, four limbs allowed the animal to move perfectly in shallow and swampy terrain, which gave Ichthyostega an evolutionary advantage. Thus, the pseudo-tetrapod could quickly attack the sea dwellers on the shores of ancient Greenland.
Skull structure
Unlike modern quadrupeds, Ichthyostega had a skull more resembling that of a typical fish. In general, the flat skull of the animal is arranged so that the lower jaw mates with the square-skull bone, as is characteristic of most reptiles. The depressions under the eyeballs are oval and shallow, located in the upper part of the central part of the skull. It is noteworthy that the torn bone in the Ichthyostega skull, unlike, for example, in humans, is adjacent not to the eye socket but to the nostril, which in turn were located at the lower section of the upper jaw. Analysis of the fossils also shows that Ichthyostega had gill covers on the backside of the skull, which fully confirms the aquatic lifestyle of the animal.
Structure of the postcranial skeleton
Although Ichthyostega had two pairs of limbs, the extinct pseudo tetrapod also had a caudal fin, which allowed it to move freely not only in shallow water but also in water. It is believed that the average length of the animal did not exceed one and a half meters, with the body ending in a long bony tail. The entire body was covered with many keratinized scales. Ichthyostega has a thorax in its abdomen, and the animals ribs could overlap, each forming a robust protective corset for the body: this was probably an adaptation to a mixed way of life. However, this skeletal structure did not allow Ichthyostega to bend its body freely. At the same time, the forelimbs were noticeably more powerful than the hind limbs, indicating the specificity of Ichthyostega gait. Each of the limbs had seven developed fingers connected by webbed tissue.
Alkyl halides, popularly known as haloalkanes or halogenoalkanes, are chemical compounds comprising at least one halogane. Although there is no clear differentiation, they are a distinctive subset of halocarbons. The compounds are widely used in different industries and, consequently, are identified by various names (Kursunlu et al., 2019). The classification of haloalkanes is based on how the halogen is connected to carbon atoms. Primary haloalkanes contain one halogen connected to an alkane group, as in the case of chloroethane. The compounds are physically characterized as hydrophobic, colorless, and odorless. The production of haloalkanes is conventionally achieved from the constituent organic compounds. The reaction used in the above case is called radical chain reaction due to the presence of an intermediary. The reaction gives rise to a set of mixtures at different stages of the reaction. The end products of the reaction can be predicted by studying the resultant bonging of the carbon and halogen atoms. The prediction can be built on the dissociation energies released as the atoms separate or join. The end products can also be predicted by looking at the possible reaction at the carbon-atom level. The dipole moments suggest it is likely to break down the compounds through distillation. Halogens can also be produced from alcohol through a nucleophilic reaction. Alcohol reacts with halogen acid to produce haloalkanes. In this case, hydrochloric acid is reacted with alkanol producing an alkyle chloride. However, if a primary acid is chosen, the reaction then needs to include an activator, as in the case of the Lucas test. Alkynes and alkenes are other synthetic sources of haloalkanes. In this case, hydrogen halides such as hydrogen bromide and hydrogen chloride react with an alkene to produce mono-haloalkanes.
Synthetic route for octane using 1-bromoheptane and iodomethane
Octane is one of the most flammable compounds found in petroleum products. It comprises hydrogen and carbon atoms, and we may not realize how we often buy this product in gas stations. This compound is a major symbol of the quality of petroleum fuels. Just like all other compounds that have low molecular weights, octane is highly flammable and volatile. Octane is an alkane and also a hydrocarbon comprised of hydrogen and carbon atoms. The chemical formula of octane is C8H18. The formula can be compressed as CH3(CH2)6CH3. Octane has several structural isomers that differ depending on the number of carbon atoms and the branching of the atoms. 1-Bromobutane (CH3(CH2)3BR reacts with a hydride to produce octane. By definition, 1-bromobutane contains one atom of bromide in its chemical formula and is colorless. However, in the presence of impurities, the liquid appears yellowish depending on the intensity of the impurities., the compound dissolves in an organic solvent but not in water. On a different note, methyl iodide, popularly known as iodomethane, is chemically denoted as CH3I. According to Parker (2017), iodomethane is emitted by rice plantations naturally. When reacted with hydrogen iodide, an iodine atom replaces one hydrogen atom producing an iodide product. The resultant product is then reacted with a hydride such as a hydrogen chloride or hydrogen bromide to produce octane. One of the hydrogen atoms in the iodomethane is displaced in the reaction; the hydride produces octane.
The reaction scheme for isomers is illustrated in the figure below.
Figure 1. Reaction scheme
Reaction mechanism and product structure
Sodium cyanide is a reactive compound of the highly reactive sodium element. The compound is comprised of sodium, carbon, and nitrogen atoms. 2-bromooctane is a complex compound comprised of carbon, hydrogen, and bromine atoms. Its chemical formula is C4H9Br. The compound is quite denser than water and has a relatively higher boiling point as compared to water. Dimethylsulfoxide (DMSO) is a human medication prescribed wit people with dietary problems. The medicine is used to contain amyloidosis, where tissues and organs collect proteins abnormality. In the reaction of sodium cyanide with 2-bromobutane, dimethyl sulfoxide acts as an aprotic solvent. Aphotic solvents contain oxygen-hydrogen bonds or nitrogen hydrogen bonds, depending on their chemical formula. The a present in the classification of the solvents suggests a lack of hydrogen atoms of protons. The aforementioned reaction produces substitution products. Roy and Saha (2018) define a substitution reaction as one in which a molecule or group of atoms from one element or compound replace their counterparts on another atom or compound respectfully. The substitution happens depending on the reactivity of the distinctive elements and the conditions required for such reactions. In our case, the (R)-2-bromooctane molecule is comprised of 8 carbon atoms, 17 hydrogen atoms, and one bromine atom. Likewise, sodium cyanide is comprised of one sodium atom, one nitrogen, and one carbon atom. The solvent four carbon atoms, six hydrogen atoms, one sulfur atom, and one oxygen atom. When (R)-2-bromooctane reacts with NaCN in the presence of DMSO, the DMSO establishes the ideal environment needed for the reactions of the two compounds (Hu et al., 2017). In the process of the reaction, the different faces of the carbon atom are equally filled. In the substitution reaction using the SN1 mechanisms, the reaction gives a mixture of 1:1 irrespective of the starting salts used in the reaction.
References
Dong, X., Peng, W., Yu, C. Y., Zhou, S., Donohoo, K. B., Tang, H., & Mechref, Y. (2019). 8-plex LC-MS/MS Analysis of Permethylated N-glycans Achieved by Using Stable Isotopic Iodomethane. Analytical Chemistry, 91(18), 11794-11802.
Hu, L., Wang, D., Chen, X., Yu, L., Yu, Y., Tan, Z., & Zhu, G. (2017). Copper-catalyzed decarboxylative methylthiolation of aromatic carboxylate salts with DMSO. Organic & biomolecular chemistry, 15(27), 5674-5679.
Kursunlu, A. N., Acikbas, Y., Ozmen, M., Erdogan, M., & Capan, R. (2019). Haloalkanes and aromatic hydrocarbons sensing using LangmuirBlodgett thin film of pillar [5] arene-biphenyl carboxylic acid. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 565, 108-117.
Roy, R., & Saha, S. (2018). Scope and advances in the catalytic propargylic substitution reaction. RSC advances, 8(54), 31129-31193.
The level of significance is usually denoted as a or alpha and refers to the probability of having the null hypothesis rejected when it is accurate or true. When the level is at 0.05, it implies that the risk of determining whether that a risk exists is 5% when there is no actual difference (Greenland, 2019). A P-value that is equal or lower than the significance level influences the rejection of the null hypothesis. Similarly, a hypothesis test tends to evaluate and analyze mutually exclusive statements to explain the one that is more likely to be correct based on the provided data. This paper evaluates the truthfulness of rejecting a 5% significance level null hypothesis when there exists a 90% specific alternative statement.
Since the alternative hypothesis has a power of 90%, the conclusion rejected the null hypothesis. The probability that the null hypothesis is true is only 5%, while 90% true for the alternative statement. This means that there are more reasons to believe that the alternative hypothesis is true relative to the contrary argument (Greenland, 2019). The validity of the alternative hypothesis influences the rejection of the null statements since it lacks sufficient evidence.
A given test is usually considered significant statistically in case the facts of the sample are unusually sufficient based on the null hypothesis. The significance level is sometimes referred to as the error rate because it is difficult to determine the accuracy of a hypothesis 100% and results depend on the position of the sample mean in the critical region. The significance level presents a statistical way of explaining the confidence in the conclusion. The 5% level is too low in comparison to 90% power for the alternative hypothesis explaining the rejection of the null statement.
In the first stage of research, the test material contents of the intestines is diluted with saline in proportion of 1 to 10, so that the solutions in dilution range from 10-1 to 10-8 are prepared. From each dilution, inoculations of different mediums are made, such as Endo plate culture media, and bismuth-sulfite agar. Next, the preparations should be incubated at 37°C for 18-24 hours.
To quantitatively characterize the aerobic microflora, a dosed inoculation on plate media from four diagnostically significant dilutions 10-4, 10-5, 10-6, 10-8 of the starting material is carried out. Dilutions are prepared in five bacteriological test tubes: 9.9 ml of isotonic sodium chloride solution for 10-3, 10-8 dilutions are poured into two test tubes, and 4.5 ml for 10-4, 10-5 dilutions into three tubes. The suspension should be sequentially transferred from the previous dilution into the subsequent one. Before work, lamellar media should be dried at a temperature of 60±1°C for 20 minutes, and at 40±1°C for 45 minutes. The microorganisms are sown on a dense canted nutrient medium. After successful sowing, the culture needs to be placed in a thermostat, where its development is monitored closely in order to properly describe the quantitative and qualitative nature of its growth.
Isolation of a Pure Culture and Its Primary Identification
In the next stage of research, isolated colonies should be selected from plate culture media and inoculated separately for the primary identification of microorganisms. García-González et al. (2018) state that Enterobacter cloacae is a ubiquitous Gram-negative, facultative anaerobic, rod-shaped bacterium belonging to the Enterobacteriaceae family (p.1). All crops are incubated at 37ºC for 18 20 hours to let the isolated colonies grow, otherwise identification of bacteria is impossible. To determine the qualitative composition of bacteria, the colonies on the plate are grouped according to the nature characteristics of each colony. This is the most significant feature of the microorganisms growth on a solid nutrient medium. The color differentiation of isolated colonies, which depends on the bacteria to differentiating components of the nutrient medium ratio, is of decisive importance in the assessment of Enterobacteriaceae on the plate media.
Gram Method Staining
In this stage of research, the results of the primary identification of bacteria are recorded and analyzed. Sowing has been already done on the medium of the minimum differentiating series to determine the genus. Most importantly, the Gram method has to be used to determine the staining ability of the cultures cells. The methods coloring is carried out as follows:
A drop of saline is applied to the defatted glass, on which the culture is suspended.
The preparation is dried and fixed over the flame of the burner, where it is held 2-3 times.
A piece of filter paper soaked in gentian violet is applied to the smear for 1-2 minutes.
The dyed filter paper is removed, without rinsing it with water.
Lugols iodine is applied to the paper for 1-2 minutes, until the smear is blackened.
Lugols iodine is removed without applying water.
A 96° alcohol solution is poured on the preparation for 20 seconds. Additionally, to exclude excessive discoloration of bacteria, iodine should be added to the solution.
The preparation is rinsed with water.
A piece of filter paper soaked in an aqueous solution of fuchsine is put on the stain for 1-2 minutes.
The dyed filter paper is removed, and the smear is rinsed with water.
The preparation is dried, then put in the microscope using the immersion oil.
The preparation is stained correctly, and the color of the culture reveals to be in the range from pink to red, thus implying that the bacteria are gram-negative, which aligns with the Enterobacteriaceae genus.
Identification Media Sowing
After the Gram method staining, the colonies are sown onto the specific identification media the combined Olkenitskys or Kliglers media. With these media, several cultures characteristics are simultaneously revealed: the ability to form hydrogen sulfide, and the relationship to glucose and lactose. Thus, the colonies are sown on both media with a bacteriological needle first along the beveled part with a stroke, and then with a prick into the thickness of the agar column. To let the cultures grow, crops are incubated at 37±1°C for 18-20 hours. Next, based on the totality of biochemical properties revealed on the combined medium, a conclusion can be made about the possible species of the culture.
In Olkenitskys medium, glucose has fermented to acid and gas, which gives the culture a yellow color with multiple discontinuities. By the combination of biochemical signs on the combined medium, several genera of Enterobacteria can be suspected simultaneously. Therefore, to establish the genus and species belonging of bacteria, the minimum differentiating series should be used. Intraspecific differentiation, as well as differentiation into biological groups, is based on differences in the fermentation of carbohydrates and the presence of amino acid decarboxylases. For example, in some cases, O- and H-antigens are serotyped.
Conclusion
The presence of Enterobacter cloacae in the substrate is indicated by hydrolysis of gelatin, as well as arginine, which is highly specific to this Enterobacteria species. On Endo medium, the cultures obtain colors in range from raspberry to pink, while on bismuth-sulfite agar they demonstrate the color range from pale green to greenish-brown. The cultures are transparent, shiny, and can be easily removed from the medium, the latter is not stained under the colonies. These qualitative characteristics indicate that the colonies present are from Enterobacteriaceae genus. All isolated strains had typical Enterobacteriaceae morphology, represented by gram-negative rods with peritrichous flagella, and grew well at 37°C on different media, which further establishes the studied culture as Enterobacter cloacae.
Alkanes are saturated hydrocarbons that have a linear or branched structure, containing only simple bonds. They include only single bonds between C-C atoms in a molecule, i.e., containing the maximum amount of hydrogen (Ackerman et al., 2018). All alkanes are substances that are similar in physical and chemical properties and differ by one or more groups of -CH2-. Such substances are called homologs, and several substances that are homologs are called homological series. The very first representative of the homologous series of alkanes is methane CH4. Next are Ethane-C2H6, Propane-C3H8, Butane-C4H10, Pentane-C5H12, Hexane-C6H14, Heptane-C7H16, and Octane-C8H18 (Shipman et al., 2016). Since all bonds are saturated to the limit, alkanes are characterized by cracking, cleavage, combustion, and halogenation reactions. Such an alkane as methane is characterized by substitution and oxidation reactions.
Chemicals such as alkanes can most often be found in petroleum products. Methane is formed due to the decomposition of the remains of plant and animal organisms without access to oxygen and is the main component of natural gas. This explains the release of gas bubbles from the bottom of swamps and reservoirs with standing water, called swamp gas. It is also released from coal seams and accumulates in mines, which is also called mine gas. Solid alkanes are part of paraffin, and the presence of carbon and hydrogen in their composition can be easily proved experimentally. Alkanes are also used to make solvents, cosmetics, and asphalt. Gaseous alkanes are used in everyday life and for the production of aerosols.
References
Ackerman, L. K., Martinez Alvarado, J. I., & Doyle, A. G. (2018). Direct CC bond formation from alkanes using Ni-photoredox catalysis. Journal of the American Chemical Society, 140(43), 14059-14063.
Califf, R. M., McCall, J., & Mark, D. B. (2017). Cosmetics, regulations, and the public health: Understanding the safety of medical and other products. JAMA internal medicine, 177(8), 1080-1082.
Finelli, C. (2019). Contribution to molecular nutrition: Carbohydrates. In Molecular Nutrition: Carbohydrates. Academic Press, 91-112.
Shipman, J., Wilson, J., Higgins, C., & & Torres, O. (2016). An Introduction to physical science (14th ed.). Cengage Learning.
Reading articles about chemistry and recent experiments in natural sciences is not always easy and interesting for many people. However, the work by Jonathan Lambert for ScienceNews about the Nobel Prize winners who built molecules in a fast and efficient way contains clear and comprehensive information. Two chemists from Germany and the United States were awarded for their independent development of organic catalysts to speed up some chemical reactions. The introduction of asymmetric organocatalysis for the construction of specific molecules helped the men take the prize of about $1 million. The members of the Nobel Committee define scientific discovery as a new element in chemistry work that has significantly changed the game. The benefits of building new molecules were perfectly described in the article, focusing on the properties of neurotoxin strychnine, drugs applicability, and other pharmaceutical details.
In my opinion, the chosen article is a successful example of how a scientific message should be delivered. Lambert does not use too many complex terms and concepts and adds simple comparisons for chemical processes. The introduction of enzymes as clunky proteins and their functions in chemical reactions or high metal costs allows the reader to understand the necessity of new molecules and why these achievements are rare in natural sciences. The names of contributors, winners, and other stakeholders are not slightly mentioned to confuse the reader. Several brief and clear descriptions strengthen the article and involve additional research. The history of chemistry is rich and varied, but its present discoveries and future perspectives have to be analyzed regularly not to miss an important project that could change the routine following properly integrated interventions. The presence of such articles in the scientific world is required to stir up the interest of individuals of different ages and social groups.
The present report aims at testing the current highway mileage of low-mileage fleet minivans of one of the automobile producers. Recently, the car manufacturer received several complaints about the highway mileage of their latest model minivan. The customers claim that the car makes less than the advertised 28 miles per gallon. The present report aims at testing if the complaints are true. For this purpose, a sample of 35 randomly-selected low-mileage fleet minivans of the latest model were elected, and their highway mileage per gallon was measured. Statistical analysis is used to understand if the actual mileage of the cars is below the advertised value.
Sample Mean, Standard Deviation, and Confidence Interval
Calculating the Confidence Interval
First, the confidence interval for the mean mileage per gallon of the minivans was calculated. In order to calculate the confidence interval, the sample size, the sample mean statistic, standard deviation, and the z value for the alpha are needed (McClaive, et al., 2018). The calculations conducted in Excel demonstrated that the sample mean was 26.72, the sample size was 2.10, the sample size was 35 minivans, and the z-value of 1.96 (for alpha of 0.05) was used).
Interpreting the Confidence Interval
The calculations demonstrated that the 95% confidence interval for the population mean was [26.02; 27.42). In other words, the mean highway mileage of the low-mileage fleet minivans lies between 26.02 and 27.42 miles per gallon with 95% certainty. The advertised mileage per gallon is 28, which is above the 95% confidence interval of the calculated population mean. This value was calculated using a sample of 35 randomly selected minivans.
The fact that the advertised mileage of the latest model of minivans is above the higher bound of the 95% confidence interval may be a sign of worry for the company. The confidence interval demonstrated that there is a high chance that the actual mileage per gallon of the new fleet lies above the actual mean mileage per gallon. Even though there is still a small chance that there is no problem with the current mileage per gallon of the new cars (McClaive, et al., 2018). However, that chance is only 5%.
Hypothesis Testing: Two-Tail Test and One-Tail Test
Calculating a Two-Tail Test
A two-tailed one-sample t-test was run to understand if the population mean differed significantly from the hypothesized value of 28. The null and the alternative hypotheses for the t-test are provided below:
H0: The population mean of the mileage per gallon of the new minivans is 28.
HA: The population mean of the mileage per gallon of the new minivans is significantly different from 28.
The results of the t-test demonstrated that the mean mileage per gallon of the new minivans (M = 26.72, SD = 2.1) was significantly different from 28 with a 95% certainty (t(34) = -3.61, p = 0.001). The t-test was conducted using excel and is submitted separately from the present report.
Interpreting the Two-Tail Test
The p-value (p = 0.001) was below the alpha level of 0.05, and the t-statistic (t(34) = -3.61) was below the critical value (-2.03) of the two-tailed test, the null hypothesis was rejected, and the alternative hypothesis was accepted (Carlson & Winquist, 2017). In other words, the test demonstrated that the population mean of the mileage per gallon of the new minivans is significantly different from the advertised value of 28 miles per gallon with a 95% certainty. This implies that the complaints of customers were not due to a chance, and the company needs to address the problem of the difference between the actual mileage per gallon and the advertised mileage per gallon.
Calculating a One-Tail Test
A one-tailed one-sample t-test was conducted to understand if the population mean mileage per gallon was significantly below the advertised value of 28. The null and alternative hypotheses for this test are provided below:
H0: The population mean of the mileage per gallon of the new minivans is 28.
HA: The population mean of the mileage per gallon of the new minivans is significantly below 28.
The results revealed that the mean mileage per gallon of the new minivans (M = 26.72, SD = 2.1) was significantly different from 28 with a 95% certainty (t(34) = -3.61, p < 0.001). The t-test was conducted using excel and is submitted separately from the present report.
Interpreting the One-Tail Test
The p-value (p = 0.001) was below the alpha level of 0.05, and the t-statistic (t(34) = -3.61) was below the critical value (-1.69) of the one-tailed test, the null hypothesis was rejected, and the alternative hypothesis was accepted (Carlson & Winquist, 2017). In other words, the test demonstrated that the population mean of the mileage per gallon of the new minivans is significantly below the advertised value of 28 miles per gallon with a 95% certainty. This implies that the complaints of customers were not due to a chance, and the company needs to address the problem of the difference between the actual mileage per gallon and the advertised mileage per gallon.
Conclusions
Methods
The results of the analysis revealed that the mean mileage per gallon in the new low-mileage minivan fleet is lower than the advertised mileage of 28 miles per gallon with at least a 95% certainty. The analysis of p-values revealed that the possibility of the mileage being different from 28 miles per gallon is 99.999%, according to the two-tailed one-sample t-test. The certainty was even higher for the one-tailed one-sample t-test (>99.999%), which implies that the possibility that the actual mean mileage of the new fleet was lower than 28 miles per gallon. Thus, it may be concluded that the one-tailed one-sample t-test provided higher certainty for addressing the problem.
According to Moore and Notz (2021), one-tailed t-tests are conducted when the researcher needs to understand if there is a difference between the population mean value and the hypothesized mean value in one direction. Since the present research aimed at understanding if the actual mileage per gallon of the new minivan fleet was lower than the advertised value of 28 miles per gallon, it was more appropriate to use a one-tailed test. Since this test provided even more certainty than the two-tailed test, it may be concluded that the actual mileage per hour was lower than that claimed by the manufacturer.
The Manufacturers Claim
The result of the analysis revealed that the manufacturers claim concerning the mileage per gallon of the new minivan fleet was wrong with a high degree of certainty. In particular, there is more than 99.99% possibility that the mean mileage per gallon of the new minivans is below 28 miles per gallon. This implies that the complaints filed by the customers are explained not by chance but by the fact that the mileage per gallon of the new cars was lower than the advertised value.
Summary
Three statistical tests were conducted to test the hypothesis that the mean value of highway mileage per hour of the new minivan fleet was below 28 miles per gallon. The calculation of 95% confidence interval revealed that the advertised mileage per gallon was above the higher bound of the confidence interval. A two-tailed one-sample t-test revealed that there was 99.999% possibility that the actual mileage per gallon was different from the advertised value, while a one-tailed one-sample t-test demonstrated that there was >99.999% possibility that the actual mileage per gallon of the new fleet was below the advertised value.
Recommendations
Since currently the company misinforms its customers about the mileage per hour of the new fleet, it is recommended to change the advertised value to 27 miles per gallon, as it was demonstrated that this value lies within the 95% confidence interval. Additionally, the company needs to inform its current customers about the findings of the present research to make amends to them to ensure customer loyalty in the future. A formal investigation is also needed to determine the reason for the discrepancies between the actual mileage per gallon and the advertised mileage per gallon.
References
Carlson, K. A., & Winquist, J. R. (2017). An introduction to statistics: An active learning approach (2nd ed.). Thousand Oaks, CA: Sage.
McClaive, J., Benson, G., & Sincich. (2018). Statistics for business and economics. Pearson.
Moore, D., & Notz., W. (2021). The Basic Practice of Statistics. Macmillan Learning.
