# Get questions and answers for Research Methods and Statistics

## GET Research Methods and Statistics TEXTBOOK SOLUTIONS

1 Million+ Step-by-step solutions Identify a piece of information that you have gained through each of the sources of knowledge discussed in this chapter (superstition and intuition, authority, tenacity, rationalism, empiricism, and science).

Provide an argument for the idea that basic research is as important as applied research.

Why is it a compliment for a scientist to be called a skeptic?

An infomercial asserts “A study proves that Fat-B-Gone works, and it will work for you also.” What is wrong with this statement?

Many psychology students believe that they do not need to know about research methods because they plan to pursue careers in clinical/counseling psychology. What argument can you provide against this view?

In a study of the effects of types of study on exam performance, subjects are randomly assigned to one of two conditions. In one condition, subjects study in a traditional manner—alone using notes they took during class lectures. In a second condition, subjects study in interactive groups with notes from class lectures. The amount of time spent studying is held constant. All students then take the same exam on the material.
a. What is the independent variable in this study?
b. What is the dependent variable in this study?
c. Identify the control and experimental groups in this study.
d. Is the independent variable manipulated, or is it a subject variable?

Researchers interested in the effects of caffeine on anxiety have randomly assigned participants to one of two conditions in a study—the nocaffeine condition or the caffeine condition. After drinking two cups of either regular or decaffeinated coffee, participants will take an anxiety inventory.
a. What is the independent variable in this study?
b. What is the dependent variable in this study?
c. Identify the control and experimental groups in this study.
d. Is the independent variable manipulated, or is it a subject variable?

Gerontologists interested in the effects of aging on reaction time have two groups of subjects take a test in which they must indicate as quickly as possible whether a probe word was a member of a previous set of words. One group of subjects is between the ages of 25 and 45, and the other group is between the ages of 65 and 85. The time it takes to make the response is measured.
a. What is the independent variable in this study?
b. What is the dependent variable in this study?
c. Identify the control and experimental groups in this study.
d. Is the independent variable manipulated, or is it a subject variable?

What should be accomplished by debriefing subjects?

Describe what is meant by “at risk” and “at minimal risk.”

In addition to treating animals in a humane manner during a study, what other guidelines does APA provide concerning using animals for research purposes?

What special ethical considerations must be taken into account when conducting research with children?

Identify the type of measure used in each of the following situations:
a. As you leave a restaurant, you are asked to answer a few questions regarding what you thought about the service you received.
b. When you join a weight-loss group, they ask that you keep a food journal noting everything that you eat each day.
c. As part of a research study, you are asked to complete a 30-item anxiety inventory.
d. When you visit your career services office, they give you a test that indicates professions to which you are best suited.
e. While eating in the dining hall one day, you notice that food services has people tallying the number of patrons selecting each entrée.
f. As part of a research study, your professor takes pulse and blood pressure measurements on students before and after completing a class exam.

Which of the following correlation coefficients represents the highest (best) reliability score?
a. + .10
b. - .95
c. + .83
d. 0.00

When you arrive for your psychology exam, you are flabbergasted to find that all of the questions are on calculus and not psychology. The next day in class, students complain so much that the professor agrees to give you all a makeup exam the following day. When you arrive in class the next day, you find that although the questions are different, they are once again on calculus. In this example, there should be high reliability of what type? What type(s) of validity is the test lacking? Explain your answers.

The librarians are interested in how the computers in the library are being used. They have three observers watch the terminals to see if students do research on the Internet, use e-mail, browse the Internet, play games, use social media sites, or do schoolwork (write papers, type homework, and so on). The three observers disagree 32 out of 75 times. What is the interrater reliability? How would you recommend that the librarians use the data?

Imagine that you want to study cell phone use by drivers. You decide to conduct an observational study of drivers by making observations at three locations—a busy intersection, an entrance/exit to a shopping mall parking lot, and a residential intersection. You are interested in the number of people who use cell phones while driving. How would you recommend conducting this study? How would you recommend collecting the data? What concerns do you need to take into consideration?

Explain the difference between participant and nonparticipant observation and disguised and undisguised observation.

How does using a narrative record differ from using a checklist?

Explain how qualitative research differs from quantitative research.

Explain the archival method.

Explain the difference between an interview and a focus group interview.

Why is action research considered an applied form of research?

The following data represent a distribution of speeds (in miles per hour) at which individuals were traveling on a highway. Organize these data into a frequency distribution with frequency (f) and relative frequency (rf) columns.

A student at your school wants to survey students regarding their credit card use. She decides to conduct the survey at the student center during lunch hour by interviewing every fifth person leaving the student center. What type of survey would you recommend she use? What type of sampling technique is being used? Can you identify a better way of sampling the student body?

Organize the data in Exercise 1 into a class interval frequency distribution using 10 intervals with frequency (f) and relative frequency (rf) columns. Which type of figure should be used to represent the data in Exercise 1â€”a bar graph, histogram, or frequency polygon? Why? Draw the appropriate figure for these data. Calculate the mean, median, and mode for the data set in Exercise 1. Is the distribution normal or skewed? If it is skewed, what type of skew is it? Which measure of central tendency is most appropriate for this distribution, and why? Calculate the mean, median, and mode for the following four distributions (a â€“ d): Calculate the range, average deviation, and standard deviation for the following five distributions:

a. 1, 2, 3, 4, 5, 6, 7, 8, 9

b. 24, 23, 22, 21, 0, 1, 2, 3, 4

c. 10, 20, 30, 40, 50, 60, 70, 80, 90

d. 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9

e. 100, 200, 300, 400, 500, 600, 700, 800, 900

The results of a recent survey indicate that the average new car costs \$23,000 with a standard deviation of \$3,500. The price of cars is normally distributed.

a. If someone bought a car for \$32,000, what proportion of cars cost an equal amount or more than this?

b. If someone bought a car for \$16,000, what proportion of cars cost an equal amount or more than this?

c. At what prcentile rank is a car that sold for \$30,000?

d. At what percentile rank is a car that sold for \$12,000?

e. What proportion of cars were sold for an amount between \$12,000 and \$30,000?

f. For what price would a car at the 16th percentile have sold?

A survey of college students was conducted during final exam week to assess the number of cups of coffee consumed each day. The mean number of cups was 5 with a standard deviation of 1.5 cups. The distribution was normal.

a. What proportion of students drank 7 or more cups of coffee per day?

b. What proportion of students drank 2 or more cups of coffee per day?

c. What proportion of students drank between 2 and 7 cups of coffee per day?

d. How many cups of coffee would an individual at the 60th percentile rank drink?

e. What is the percentile rank for an individual who drinks 4 cups of coffee a day?

f. What is the percentile rank for an individual who drinks 7.5 cups of coffee a day?

Fill in the missing information in the following table representing performance on an exam that is normally distributed with XÌ… = 72 and S = 9. A health club recently conducted a study of its members and found a positive relationship between exercise and health. It was claimed that the correlation coefficient between the variables of exercise and health was +1.25. What is wrong with this statement? In addition, it was stated that this proved that an increase in exercise increases health. What is wrong with this statement?

Draw a scatterplot indicating a strong negative relationship between the variables of income and mental illness. Be sure to label the axes correctly.

We have mentioned several times that there is a fairly strong positive correlation between SAT scores and freshman GPAs. The admissions process for graduate school is based on a similar test, the GRE, which also has a potential 400 to 1600 total point range. If graduate schools do not accept anyone who scores below 1000 and if a GPA below 3.00 represents failing work in graduate school, what would we expect the correlation between GRE scores and graduate school GPAs to be like in comparison to the correlation between SAT scores and college GPAs? Why would we expect this?

In a study on caffeine and stress, college students indicated how many cups of coffee they drink per day and their stress level on a scale of 1 to 10. The data are provided in the following table.

Number of Cups of Coffee                                          Stress Level

3………………………………………………………………………………………….5

2………………………………………………………………………………………….3

4………………………………………………………………………………………….3

6………………………………………………………………………………………….9

5………………………………………………………………………………………….4

1………………………………………………………………………………………….2

7………………………………………………………………………………………..10

3………………………………………………………………………………………….5

2………………………………………………………………………………………….3

4………………………………………………………………………………………….8

Calculate a Pearson’s r to determine the type and strength of the relationship between caffeine and stress level. How much of the variability in stress scores is accounted for by the number of cups of coffee consumed per day?

Given the following data, determine the correlation between IQ scores and psychology exam scores, between IQ scores and statistics exam scores, and between psychology exam scores and statistics exam scores. Calculate the coefficient of determination for each of these correlation coefficients, and explain what it means. In addition, calculate the regression equation for each pair of variables.

Assuming that the regression equation for the relationship between IQ score and psychology exam score is Yâ€² = 9 + 0.274X, what would you expect the psychology exam scores to be for the following individuals given their IQ exam scores? Imagine that I have a jar that contains 50 blue marbles and 20 red marbles.

a. What is the probability of selecting a red marble from the jar?

b. What is the probability of selecting a blue marble from the jar?

c. What is the probability of selecting either a red or a blue marble from the jar?

d. What is the probability of selecting a red marble (with replacement) followed by a blue marble?

What is the probability of a couple having children in the following birth order: boy, boy, boy, boy?

What is the probability of selecting either a 2 or a 4 (of any suit) from a standard deck of cards?

If height is normally distributed with a mean of 68 inches and a standard deviation of 5 inches, what is the probability of selecting someone who is 70 inches or taller?

For the distribution described in exercise 4, what is the probability of selecting someone who is 64 inches or shorter?

Data from exercise 4

If height is normally distributed with a mean of 68 inches and a standard deviation of 5 inches, what is the probability of selecting someone who is 70 inches or taller?

For the distribution described in exercise 4, what is the probability of selecting someone who is 70 inches or taller or 64 inches or shorter?

Data from exercise 4

If height is normally distributed with a mean of 68 inches and a standard deviation of 5 inches, what is the probability of selecting someone who is 70 inches or taller?

For the distribution described in exercise 4, what is the probability of selecting someone who is 70 inches or taller followed by someone who is 64 inches or shorter?

Data from exercise 4

If height is normally distributed with a mean of 68 inches and a standard deviation of 5 inches, what is the probability of selecting someone who is 70 inches or taller?

The admissions counselors at Brainy University believe that the freshman class they have just recruited is the brightest yet. If they want to test this belief (that the freshmen are brighter than the other classes), what are the null and alternative hypotheses? Is this a one- or two tailed hypothesis test?

To test the hypothesis in exercise 8, the admissions counselors select a random sample of freshmen and compare their scores on the SAT with those of the population of upperclassmen. They find that the freshmen do in fact have a higher mean SAT score. However, they are unaware that the sample of freshmen was not representative of all freshmen at Brainy University. In fact, the sample overrepresented those with high scores and underrepresented those with low scores. What type of error (Type I or Type II) did the counselors make?

A researcher believes that family size has increased in the past decade in comparison to the previous decade—that is, people are now having more children than they were before. What are the null and alternative hypotheses in a study designed to assess this? Is this a one- or two-tailed hypothesis test?

What are the appropriate H0 and Ha for each of the following research studies? In addition, note whether the hypothesis test is one- or two-tailed.

a. A study in which researchers want to test whether there is a difference in spatial ability between left- and right-handed people

b. A study in which researchers want to test whether nurses who work 8-hour shifts deliver higher-quality care than those who work 12-hour shifts

c. A study in which researchers want to determine whether crate-training puppies is superior to training without a crate

Assume that each of the following conclusions represents an error in hypothesis testing. Indicate whether each of the statements is a Type I or II error.

a. Based on the data, the null hypothesis is rejected.

b. There is no significant difference in quality of care between nurses who work 8- and 12-hour shifts.

c. There is a significant difference between right- and left-handers in their ability to perform a spatial task.

d. The researcher fails to reject the null hypothesis based on these data.

How do inferential statistics differ from descriptive statistics?

A researcher is interested in whether students who attend private high schools have higher average SAT scores than students in the general population. A random sample of 90 students at a private high school is tested and has a mean SAT score of 1050. The average score for public high school students is 1000 (σ = 200).

a. Is this a one- or two-tailed test?

b. What are H0 and Ha for this study?

c. Compute zobt.

d. What is zcv?

e. Should H0 be rejected? What should the researcher conclude?

f. Determine the 95% confidence interval for the population mean, based on the sample mean.

The producers of a new toothpaste claim that it prevents more cavities than other brands of toothpaste. A random sample of 60 people used the new toothpaste for 6 months. The mean number of cavities at their next checkup is 1.5. In the general population, the mean number of cavities at a 6-month checkup is 1.73 (σ = 1.12).

a. Is this a one- or two-tailed test?

b. What are H0 and Ha for this study?

c. Compute zobt.

d. What is zcv?

e. Should H0 be rejected? What should the researcher conclude?

f. Determine the 95% confidence interval for the population mean, based on the sample mean.

Why does tcv change when the sample size changes? What must be computed to determine tcv?

Henry performed a two-tailed test for an experiment in which N = 24. He could not find his table of t critical values, but he remembered the tcv at df = 13. He decided to compare his tobt with this tcv. Is he more likely to make a Type I or a Type II error in this situation?

A researcher hypothesizes that people who listen to music via headphones have greater hearing loss and will thus score lower on a hearing test than those in the general population. On a standard hearing test, the overall mean is 22.5. The researcher gives this same test to a random sample of 12 individuals who regularly use headphones. Their scores on the test are 16, 14, 20, 12, 25, 22, 23, 19, 17, 17, 21, 20.

a. Is this a one- or two-tailed test?

b. What are H0 and Ha for this study?

c. Compute tobt.

d. What is tcv?

e. Should H0 be rejected? What should the researcher conclude?

f. Determine the 95% confidence interval for the population mean, based on the sample mean.

A researcher hypothesizes that individuals who listen to classical music will score differently from the general population on a test of spatial ability. On a standardized test of spatial ability, μ = 58. A random sample of 14 individuals who listen to classical music is given the same test. Their scores on the test are 52, 59, 63, 65, 58, 55, 62, 63, 53, 59, 57, 61, 60, 59.

a. Is this a one- or two-tailed test?

b. What are H0 and Ha for this study?

c. Compute tobt.

d. What is tcv?

e. Should H0 be rejected? What should the researcher conclude?

f. Determine the 95% confidence interval for the population mean, based on the sample mean.

You read in a health magazine about a study in which a new therapy technique for depression was examined. A group of depressed individuals volunteered to participate in the study, which lasted 9 months. There were 50 subjects at the beginning of the study and 29 at the end of the 9 months. The researchers claimed that of those who completed the program, 85% improved. What possible confounds can you identify in this study?

On the most recent exam in your biology class, every student earned an A. The professor claims that he must really be a good teacher for all of the students to have done so well. Given the confounds discussed in this chapter, what alternative explanation can you offer for this result?

What are internal validity and external validity, and why are they so important to researchers?

A college student is interested in whether there is a difference between male and female students in the amount of time they spend studying each week. The student gathers information from a random sample of male and female students on campus. The amounts of time spent studying are normally distributed. The data are:

Males                                                   Females

27……………………………………………………….25

25……………………………………………………….29

19……………………………………………………….18

10……………………………………………………….23

16……………………………………………………….20

22……………………………………………………….15

14……………………………………………………….19

a. What statistical test should be used to analyze these data?

b. Identify H0 and Ha for this study.

c. Conduct the appropriate analysis.

d. Should H0 be rejected? What should the researcher conclude?

e. If significant, compute and interpret the effect size.

f. If significant, draw a graph representing the data.

g. Determine the 95% confidence interval.

A student is interested in whether students who study with music playing devote as much attention to their studies as do students who study under quiet conditions (he believes that studying under quiet conditions leads to better attention). He randomly assigns participants to either the music or no-music condition and has them read and study the same passage of information for the same amount of time. Subjects are given the same 10-item test on the material. Their scores appear next. Scores on the test represent interval-ratio data and are normally distributed.

Music                                                    No Music

6…………………………………………………………..10

5…………………………………………………………….9

6…………………………………………………………….7

5…………………………………………………………….7

6…………………………………………………………….6

6…………………………………………………………….6

7…………………………………………………………….8

8…………………………………………………………….6

5…………………………………………………………….9

a. What statistical test should be used to analyze these data?

b. Identify H0 and Ha for this study.

c. Conduct the appropriate analysis.

d. Should H0 be rejected? What should the researcher conclude?

e. If significant, compute and interpret the effect size.

f. If significant, draw a graph representing the data.

g. Determine the 95% confidence interval.

A researcher is interested in whether listening to classical music improves spatial ability. She randomly assigns subjects to either a classical music condition or a no-music condition. Is this a between-subjects or a within-subjects design?

How does using a Latin square aid a researcher in counterbalancing a study?

What are the similarities and differences between within-subjects and matched-subjects designs?

A researcher is interested in whether participating in sports positively influences self-esteem in young girls. She identifies a group of girls who have not played sports before but are now planning to begin participating in organized sports. The researcher gives them a 50-item self-esteem inventory before they begin playing sports and administers the same test again after 6 months of playing sports. The self-esteem inventory is measured on an interval scale, with higher numbers indicating higher self-esteem. In addition, scores on the inventory are normally distributed. The scores follow.

Before                                                                  After

44……………………………………………………………….46

40……………………………………………………………….41

39……………………………………………………………….41

46……………………………………………………………….47

42……………………………………………………………….43

43……………………………………………………………….45

a. What statistical test should be used to analyze these data?

b. Identify H0 and Ha for this study.

c. Conduct the appropriate analysis.

d. Should H0 be rejected? What should the researcher conclude?

e. If significant, compute and interpret the effect size.

f. If significant, draw a graph representing the data.

g. Determine the 95% confidence interval.

The researcher in exercise 5 in Chapter 9 decides to conduct the same study using a within-subjects design to control for differences in cognitive ability. He selects a random sample of subjects and has them study different material of equal difficulty in both the music and no-music conditions. The study is completely counterbalanced to control for order effects. The data appear next. As in Chapter 9, they are measured on an interval-ratio scale and are normally distributed; he believes that studying under quiet conditions will lead to better performance.

Music                                    No Music

7……………………………………………….7

6……………………………………………….8

5……………………………………………….7

6……………………………………………….7

8……………………………………………….9

8……………………………………………….8

a. What statistical test should be used to analyze these data?

b. Identify H0 and Ha for this study.

c. Conduct the appropriate analysis.

d. Should H0 be rejected? What should the researcher conclude?

e. If significant, compute and interpret the effect size.

f. If significant, draw a graph representing the data.

g. Determine the 95% confidence interval.

What is/are the advantage(s) of conducting a study with three or more levels of the independent variable?

What is the difference between a randomized ANOVA and a repeated measures ANOVA? What does the term one-way mean with respect to an ANOVA?

Explain between-groups variance and within-groups variance.

If a researcher decides to use multiple comparisons in a study with three conditions, what is the probability of a Type I error across these comparisons? Use the Bonferroni adjustment to determine the suggested alpha level.

If H0 is true, what should the F-ratio equal or be close to? If Ha is supported, should the F-ratio be greater than, less than, or equal to 1?

When should post hoc comparisons be performed?

What information does eta-squared (η2) provide?

Why is a repeated measures ANOVA statistically more powerful than a randomized ANOVA?

A researcher conducts a study of the effects of amount of sleep on creativity. The creativity scores for four levels of sleep (2 hours, 4 hours, 6 hours, and 8 hours) for N = 20 subjects are presented here. a. Complete the following ANOVA summary table. (If your instructor wants you to calculate the sums of squares, use the preceding data to do so.) b. Is Fobt significant at Î± = .05; at Î± = .01?

c. Perform post hoc comparisons if necessary.

d. What conclusions can be drawn from the F-ratio and the post hoc comparisons?

e. What is the effect size, and what does this mean?

f. Graph the means.

In a study of the effects of stress on illness, a researcher tallied the number of colds people contracted during a 6-month period as a function of the amount of stress they reported during that same time period. There were three stress levels: minimal, moderate, and high stress. The sums of squares appear in the following ANOVA summary table. The mean for each condition and the number of subjects per condition are also noted. a. Complete the ANOVA summary table.

b. Is Fobt significant at Î± = .05? at Î± = .01?

c. Perform post hoc comparisons if necessary.

d. What conclusions can be drawn from the F-ratio and the post hoc comparisons?

e. What is the effect size, and what does this mean?

f. Graph the means.

A researcher interested in the effects of exercise on stress had participants exercise for 30, 60, or 90 minutes per day. The mean stress level on a 100-point stress scale (with 100 indicating high stress) for each condition appears next, along with the ANOVA summary table with the sums of squares indicated. a. Complete the ANOVA summary table.

b. Is Fobt significant at Î± = .05; at Î± = .01?

c. Perform post hoc comparisons if necessary.

d. What conclusions can be drawn from the F-ratio and the post hoc comparisons?

e. What is the effect size, and what does this mean?

f. Graph the means.

A researcher conducted an experiment on the effects of a new drug on depression. The researcher had a control group that received nothing, a placebo group, and an experimental group that received the drug. A depression inventory that provided a measure of depression on a 50-point scale was used (50 indicates that an individual is very high on the depression variable). The ANOVA summary table appears next, along with the mean depression score for each condition. a. Complete the ANOVA summary table.

b. Is Fobt significant at a = .05; at a = .01?

c. Perform post hoc comparisons if necessary.

d. What conclusions can be drawn from the F-ratio and the post hoc comparisons?

e. What is the effect size, and what does this mean?

f. Graph the means.

A researcher is interested in the effects of practice on accuracy in a signal-detection task. Subjects are tested with no practice, after 1 hour of practice, and after 2 hours of practice. Each person participates in all three conditions. The following data indicate how many signals each participant detected accurately at each level of practice.  a. Complete the ANOVA summary table. (If your instructor wants you to calculate the sums of squares, use the preceding data to do so.)

b. Is Fobt significant at Î± = .05? at Î± = .01?

c. Perform post hoc comparisons if necessary.

d. What conclusions can be drawn from the F-ratio and the post hoc comparisons?

e. What is the effect size, and what does this mean?

f. Graph the means.

A researcher has been hired by a pizzeria to determine which type of crust customers prefer. The restaurant offers three types of crust: hand-tossed, thick, and thin. Following are the mean number of 1-inch pieces of pizza eaten for each condition from 10 subjects who had the opportunity to eat as many pieces with each type of crust as they desired. The ANOVA summary table also follows. a. Complete the ANOVA summary table.

b. Is Fobt significant at Î± = .05? at Î± = .01?

c. Perform post hoc comparisons if necessary.

d. What conclusions can be drawn from the F-ratio and the post hoc comparisons?

e. What is the effect size, and what does this mean?

f. Graph the means.

A researcher is interested in whether massed or spaced studying has a greater impact on grades in a course. The researcher has her class study for 6 hours all in one day for one exam (massed study condition). She has them study for 2 hours each day for 3 days for another exam (3-day spaced condition). Last, she has them study for 1 hour a day for 6 days for a third exam (6-day spaced condition). The mean exam score (out of a possible 100 points) for each condition appears next, along with the ANOVA summary table. a. Complete the ANOVA summary table.

b. Is Fobt significant at Î± = .05; at Î± = .01?

c. Perform post hoc comparisons if necessary.

d. What conclusions can be drawn from the F-ratio and the post hoc comparisons?

e. What is the effect size, and what does this mean?

f. Graph the means.

What is the advantage of manipulating more than one independent variable in an experiment?

How many independent variables are in a 4 × 6 factorial design? How many conditions (cells) are in this design?

In a study, a researcher manipulated the number of hours that participants studied (either 4, 6, or 8), the type of study technique they used (shallow processing versus deep processing), and whether subjects studied individually or in groups. What is the factorial notation for this design?

What is the difference between a cell (condition) mean and the means used to interpret a main effect?

How many main effects and interaction effects are possible in a 2 × 6 factorial design?

Which of the following is the best operational definition of depression?
a. Depression is defined as that low feeling you get sometimes.
b. Depression is defined as what happens when a relationship ends.
c. Depression is defined as your score on a 50-item depression inventory.
d. Depression is defined as the number of boxes of tissues that you cry your way through.

Explain when you would use the Friedman test versus the Wilcoxon matched-pairs signed-ranks T test.

Imagine that marketing researchers working for a food company want to determine whether children would prefer ketchup of a different color. They develop red, green, and blue ketchups that all taste the same and have children (N = 7) taste each of the ketchups (a correlated groups design) and rank them on a 5-point scale with 5 indicating the highest preference. The data from the 7 subjects appear below: a. What statistical test should be used to analyze these data?

b. Identify H0 and Ha for this study.

c. Conduct the appropriate analysis.

d. Should H0 be rejected? What should the researcher conclude?

What information is contained on the title page of a manuscript?

Briefly describe the type of information that should be in an introduction.

Identify the grammatical or formatting errors in each of the following statements:

a. 50 students participated in the study.

b. The F-score was 6.54 with a p-value of .05 and 1 and 12 degrees of freedom.

c. The data is presented in Table 1.

d. One group of participants took the medication while the other group did not.

Table 15.1 Explain when you would use the Kruskal-Wallis test versus the Wilcoxon rank-sum test.

Imagine that the researchers in exercise 6 want to conduct the same study as a within-subjects design. Participants rate both the green and red sauces by indicating the tastiness on a 10-point scale. As in exercise 6, researchers are concerned that the color of the green sauce will adversely affect tastiness scores. Tastiness scores tend to be skewed. The scores follow.

a. What statistical test should be used to analyze these data?

b. Identify H0 and Ha for this study.

c. Conduct the appropriate analysis.

d. Should H0 be rejected? What should the researcher conclude

Researchers at a food company are interested in how a new spaghetti sauce made from green tomatoes (and green in color) will compare to their traditional red spaghetti sauce. They are worried that the green color will adversely affect the tastiness scores. They randomly assign subjects to either the green or red sauce condition. Participants indicate the tastiness of the sauce on a 10-point scale. Tastiness scores tend to be skewed. The scores follow:

Red Sauce                                           Green Sauce

7………………………………………………………………….4

6………………………………………………………………….5

9………………………………………………………………….6

10………………………………………………………………..8

6………………………………………………………………….7

7………………………………………………………………….6

8………………………………………………………………….9

a. What statistical test should be used to analyze these data?

b. Identify H0 and Ha for this study.

c. Conduct the appropriate analysis.

d. Should H0 be rejected? What should the researcher conclude?

A researcher is interested in comparing the maturity level of students who volunteer for community service versus those who do not. The researcher assumes that those who perform community service will have higher maturity scores. Maturity scores tend to be skewed (not normally distributed). The maturity scores appear next. Higher scores indicate higher maturity levels.

No Community Service                                 Community Service

33………………………………………………………………………….41

41………………………………………………………………………….48

54………………………………………………………………………….61

13………………………………………………………………………….72

22………………………………………………………………………….83

26………………………………………………………………………….55

a. What statistical test should be used to analyze these data?

b. Identify H0 and Ha for this study.

c. Conduct the appropriate analysis.

d. Should H0 be rejected? What should the researcher conclude?

A teacher believes that the percentage of students at her high school who go on to college is higher than the rate in the general population of high school students. The rate in the general population is 30%. In the most recent graduating class at her high school, the teacher found that 90 students graduated and that 40 of those went on to college.

a. What is χ2obt?

b. What is df for this test?

c. What is χ2cv?

d. What conclusion should be drawn from these results?

You notice in your introductory psychology class that more women tend to sit up front, and more men sit in the back. To determine whether this difference is significant, you collect data on the seating preferences for the students in your class. The data follow: a. What is Ï‡2obt?

b. What is df for this test?

c. What is Ï‡2cv?

d. What conclusion should be drawn from these results?

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