# QUALITATIVE RESEARCH

August 30, 2017

Question
Part I

Jackson, Sherri L. (2012). Research methods and statistics: A critical thinking approach. Fourth ed.

pp220-221. Even exercises.

2. 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 (? = 1.12).

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

b. What are Ho and Ha for this study?

c. Compute zobt .

d. What is zcv?

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

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

4. 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 tcvat df = 13. He decided to compare his tobtwith this tcv. Is he more likely to make a Type I error or a Type II error in this situation?

6. A researcher Hypothesizes that individuals who listen to classical music will score differently from the general population on a test of special 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 Ho and Ha for this study?

c. Compute tobt .

d. What is tcv?

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

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

8. A researcher believes that the percentage of people who exercise in California is greater than the national exercise rate. The national rate is 20%. The researcher gathers a random sample of 120 individuals who live in California and finds that the number who exercise regularly is 31 out of 120.

a. What is x2obt?

b. What is df for this test?

c. What is x2cv?

d. What conclusion should be drawn from these results?

//

Jackson S. L. pp 273 – 275. Even exercises.

2. 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.

4. The researcher in exercise 2 decides to conduct the same study using a with-in participants 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 counter balanced to control for order effects. The data appear next. As before, 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.

6. 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?

8. 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.

Men Women

Front of the Room 15 27

Back of the Room 32 19

a. What is x2obt ?

b. What is df for this test?

c. What is x2cv ?

d. What conclusion should be drawn from these results?

Part 2 (use citations as required)

1. What are degrees of freedom? How are the calculated?

What do inferential statistics allow you to infer?
What is the General Linear Model (GLM)? Why does it matter?
Compare and contrast parametric and nonparametric statistics. Why and in what types of cases would you use one over the other?
Why is it important to pay attention to the assumptions of the statistical test? What are your options if your dependent variable scores are not normally distributed?
Part 3
Part II introduces you to a debate in the field of education between those who support Null Hypothesis Significance Testing (NHST) and those who argue that NHST is poorly suited to most of the questions educators are interested in. Jackson (2012) and Trochim and Donnelly (2006) pretty much follow this model. Northcentral follows it. But, as the authors of the readings for Part II argue, using statistical analyses based on this model may yield very misleading results. You may or may not propose a study that uses alternative models of data analysis and presentation of findings (e.g., confidence intervals and effect sizes) or supplements NHST with another model. In any case, by learning about alternatives to NHST, you will better understand it and the culture of the field of education.