# PSYCHOLOGY STATISTICS

PSYC 355

SPSS Homework 1 Instructions: One-Sample t Tests and Paired-Samples t Tests (40 points)

When submitting this file, be sure the filename includes your full name, course and section. Example: HW1_JohnDoe_355B03

Please note that for all problems in this course, the standard cut-off (alpha) for a test of significance will be .05 unless otherwise noted in the problem. Also, remember that we divide the p value in half when reporting on one-tailed tests.

Part One:

Problem Set 1: The single-sample t test

File: Open “Module 1 Exercise File 1” found in Blackboard Course Content (Course Guides and Assignment Instructions—Assignment Instructions—SPSS Homework—SPSS Homework 1 Files).

Research Scenario: A clinical psychologist conducts group therapy with military veterans and wants to determine whether their scores on the Revised UCLA Loneliness Scale (R-UCLA-LS; Russell et al., 1980) are different from those in the general population. She administers the R-UCLA-LS to a group of 12 veterans and enters their scores into an SPSS data file (Exercise File 1). She knows that the population mean on the R-UCLA Loneliness Scale is 37, with higher scores indicating higher levels of loneliness. Conduct a single-sample t test to determine whether combat veterans score differently than the general population on the R-UCLA-LS.

Respond to the following items:

1. Paste SPSS output (2 pts). Beneath the output, type the answers to the following questions:

a. Mean R-UCLA-LS score for the sample of veterans (2 pts)

b. Standard deviation of the scores for the sample of veterans (2 pts)

c. p value (significance) of the test (2 pts)

2. Create a histogram that demonstrates the distribution of scores. Be sure to correctly label the X and Y axes and give your graph a title. (2 pts)

3. Write an APA-style Results section based on your analysis. All homework Results sections should follow the example given in the SPSS tutorials. Remember to include a decision about the null hypothesis. (3 pts)

Problem Set 2: The paired-samples t test

File: Open “Module 1 Exercise File 2” found in Blackboard Course Content (Course Guides and Assignment Instructions—Assignment Instructions—SPSS Homework—SPSS Homework 1 Files).

Research Scenario: A researcher is interested in whether pairs of identical twins have different SAT scores in late high school. She collects scores from a sample of 10 pairs of twins and enters them into an SPSS data file, labeling the groups as “Twin 1” and “Twin 2” (Exercise File 2). Conduct a paired-samples t test to determine whether there is a difference in SAT scores between twins.

Respond to the following items:

1. Paste SPSS output (2 pts). Beneath the output, type the answers to the following questions (2 pts. each):

a. Based on the research scenario, is the likely null hypothesis for this study that twins will score a) the same or b) differently on the SAT? Choose one, and use the information you have learned about hypothesis testing (from reading, presentations, PSYC 354 etc.) to support your answer.

b. Based on the SPSS output, what is the mean SAT score of the “Twin 1” group?

c. Based on the SPSS output, what is the standard deviation of the “Twin 2” group?

2. Create a boxplot that illustrates the differences between the groups of twins. (2 pts)

3. Write an APA-style Results section based on your analysis. All homework “Results sections” should follow the example given in the SPSS tutorials. Remember to include a decision about the null hypothesis. (3 pts)

Part Two:

Problem Set 1: The single-sample t test

Research Scenario: A college professor administers a vocational interest inventory to a sample of math majors at the university where he teaches. He believes that they will have higher scores on the “Analytical” scale than students in the general population, who normally score a 38. The table below shows the scores of the math majors on the “Analytical” scale of the vocational interest inventory. Using the table, enter the data into a new SPSS file and conduct a one-sample t test to evaluate whether these scores are significantly higher than those of the general population of college students.

The steps of the test will be the same as the ones you have been practicing in Part One of the assignment—the only difference is that you are now responsible for creating the data file as well. Remember to name and define your variables under the “Variable View,” then return to the “Data View” to enter and analyze the data.