Are there circumstances when researchers do not want to reject the null hypothesis, or is it always the case that statistical hypothesis testing is aimed at rejecting the null hypothesis? Explain your answer.

1. In a fictional study, a pretest–posttest design was used to examine the influence of a television program on children’s aggressiveness. The number of aggressive responses was measured during an observation period both before and after the television program.
Participant Before After
1 6 9
2 4 3
3 12 11
4 9 12
5 10 14
6 2 6
7 14 12
a. What is the independent variable? How many levels? What are the levels of the
IV
b. What is the dependent variable?
c. Which type of hypothesis test you would use and why.
d. Using the knowledge you have acquired in PS211, follow all the appropriate steps to determine if there is a significant difference between the levels of the independent variable.
e. As a student of statistics, what things must you keep in mind when interpreting the results?

2. Dr. Hogan was interested in the effects of test anxiety on concentration abilities. He measured student anxiety levels when the students arrived at his laboratory and then again immediately before taking an examination using an anxiety questionnaire. Dr. Hogan
hypothesized that participants in his study would have higher anxiety scores immediately prior to the completion of the exam compared to when they first came in. As hypothesized, Dr. Hogan found that participants’ anxiety scores were significantly higher immediately prior to the examination compared to baseline scores. As a result of this information, what type of t test was Dr. Hogan MOST likely to use to test his hypothesis? Is Dr. Hogan’s hypothesis test one-tailed or two-tailed? Explain your answers.

3. Are there circumstances when researchers do not want to reject the null hypothesis, or is it always the case that statistical hypothesis testing is aimed at rejecting the null hypothesis? Explain your answer.

4. Recent research by Wilson and Daly (2006) tested the idea that juvenile criminal offenders think less about future consequences than do noncriminal juveniles. To test the idea that juvenile offenders discount future consequences of their behavior, the researchers had juvenile offenders and nonoffenders engage in a decision task with real monetary consequences. The researchers found that the proportion of “future discounting” participants did not differ for the two groups. (a) Identify the populations. (b) What is the appropriate hypothesis test to be used for analyzing the data, and what is the comparison distribution? (c) Evaluate whether the assumptions for the hypothesis test are met in this study.

5. 2. A researcher presented the findings of a study at a local conference. In the study, the researcher investigated the impact of heat stress on the performance of test-takers. She thought that test-takers exposed to high levels of heat in a temperature-controlled room would make significantly more errors compared to test-takers in a standard-temperature temperature-controlled room but used a non-directional hypothesis test. Prior to testing, the researcher conducted a power analysis and found that she needed 46 participants to have sufficient power. At the conference, the researcher reported the following results: t(44) =2.33, p < 0.05, Cohen’s d = 0.90. The researcher was quite confident in her findings and concluded that temperature affects test-taking performance and that the effect should be factored into scoring exams. Another researcher at the conference criticized the researcher’s results, citing another study that found evidence to the contrary. How could the original researcher defend her results?

6. Does the average salary of third basemen differ from that of shortstops? Five third basemen and five shortstops were selected at random from the National League. Their 2015 season salaries (in millions of dollars) appear in the table.
Third Baseman Shortstop
1.300 0.316
0.316 0.322
3.000 3.850
0.525 0.700
0.425 4.600
a. What is the independent variable? How many levels? What are the levels of the IV
b. What is the dependent variable?
c. Which type of hypothesis test you would use and why.
d. Using the knowledge you have acquired in PS211, follow all the appropriate steps to determine if there is a significant difference between the levels of the independent variable.

7. Dr. Johnson conducted an independent-samples t test to explore the effect of gender on treatment outcomes. On examination for assumptions, Dr. Johnson, who had a sample size of 88 participants, found that the scores for men and women were positively skewed. Thus, the data did not meet the assumption of normality. Can Dr. Johnson continue interpreting the results of her independent-samples t test even though the assumption was violated? Why or why not? How should Dr. Johnson proceed?

8. A researcher was interested in whether female actors would be higher in extroversion or neuroticism personality traits. A number of female acting students from across the country were randomly sampled to take part in the experiment. They were all given two subscales from the Big Five Inventory (BFI; John & Srivastava, 1999). The scale measures five different personality subtypes – openness to experience, conscientiousness, extroversion, agreeableness, and neuroticism. The Extroversion and Neuroticism subscales contain 8 questions each, with scores ranging from 8 – 40. A lower score means a person exhibits less of the personality trait than a higher number.

Below is an SPSS output for the analysis. A) explain what type of test was performed and why, B) explain the information represented in each table and each column, C) report the findings in APA format and D) interpret the findings using a well-crafted paragraph write
up.