Time to Practice – Week Three

Complete both Part A and Part B below.

Part A

Some questions in Part A require that you access data from Statistics for People Who (Think They) Hate Statistics . This data is available on the student website under the Student Test Resources link.

1. For the following research questions, create one null hypothesis, one directional research hypothesis, and one nondirectional research hypothesis.

a. What are the effects of attention on out-of-seat classroom behavior?

b. What is the relationship between the quality of a marriage and the quality of the spouses’ relationships with their siblings?

c. What is the best way to treat an eating disorder?

2. Provide one research hypothesis and an equation for each of the following topics:

a. The amount of money spent on food among undergraduate students and undergraduate student-athletes

b. The average amount of time taken by white and brown rats to get out of a maze

c. The effects of Drug A and Drug B on a disease

d. The time to complete a task in Method 1 and Method 2

3. Why does the null hypothesis presume no relationship between variables?

4. Create a research hypothesis tested using a one-tailed test and a research hypothesis tested using a two-tailed test.

5. What does the critical value represent?

6. Given the following information, would your decision be to reject or fail to reject the null hypothesis? Setting the level of significance at .05 for decision making, provide an explanation for your conclusion.

a. The null hypothesis that there is no relationship between the type of music a person listens to and his crime rate (p < .05).

b. The null hypothesis that there is no relationship between the amount of coffee consumption and GPA (p = .62).

c. The null hypothesis that there is a negative relationship between the number of hours worked and level of job satisfaction (p = .51).

7. Why is it harder to find a significant outcome (all other things being equal) when the research hypothesis is being tested at the .01 rather than the .05 level of significance?

8. Why should we think in terms of “failing to reject” the null rather than just accepting it?

9. When is it appropriate to use the one-sample z test?

10. What similarity does a z test have to a simple z or standard score?

11. For the following situations, write out a research hypothesis:

a. Bob wants to know if the weight loss for his group on the chocolate-only diet is representative of weight loss in a large population of middle-aged men.

b. The health department is charged with finding out if the rate of flu per thousand citizens for this past flu season is comparable to the average rate of the past 50 seasons.

c. Blair is almost sure that his monthly costs for the past year are not representative of his average monthly costs over the past 20 years.

12. There were about 15 flu cases per week, this flu season, in the Oshkosh school system. The weekly average for the entire state is 16 and the standard deviation, is 2.35. Are the kids in Oshkosh as sick as the kids throughout the state?

From Salkind (2011). Copyright © 2012 SAGE. All Rights Reserved. Adapted with permission.

Part B

Complete the following questions. Be specific and provide examples when relevant.

Cite any sources consistent with APA guidelines.

Question

Answer

The average raw math achievement score for third graders at a Smith elementary school is 137; third graders statewide score an average of 124 with a standard deviation of 7. Are the Smith third graders better at math than third graders throughout the state? Perform the correct statistical test, applying the eight steps of the hypothesis testing process as demonstrated on pp. 185–187 of Statistics for People Who (Think they) Hate Statistics.

What is a research question that you would like to answer? Write the null and research hypotheses. Would you use a one- or two-tailed test? Why?

What do we mean when we say that a statistical result is significant? What is the difference between a statistically significant and a meaningful result? Why is statistical significance important?

Describe a Type I error for the previous study that compares third graders’ math achievement. Describe a Type II error for that study.