Psych 241

Homework 5: Statistics

In this assignment, you will use SPSS on a PC in one of the campus computer labs to perform the assigned analyses. The first thing you must do is download the data file. Right-click (click with the right-hand mouse button) on this link: homework5-data-labeled.txt and select “Save target as.” Save the data file to your desktop so that you can find it.

Next, start SPSS from the Start menu on your PC. If the dialog box appears, select "Open an existing data source." (If the dialog box does not appear, then select “open data” from the menu at the top of the SPSS window.) Click "OK". Under "Files of type" select "Text (*.txt)". Then find the file "homework5-data-labeled.txt" that you saved to the desktop and click on it. Click "Open". Then give the following answers to the import wizard:

· Does your text file match a predefined format? NO (click "Next")

· How are your variables arranged? Delimited

· Are variable names included at the top of your file? Yes (then click "Next)

· Then simply click "Next" on each additional page until "Finish" appears at the bottom. Click "Finish."

The file contains fictitious data for 30 subjects (one per row). There are 5 columns as follows:

Column	Variable name	Description of variable
1.	ID	Subject number
2.	sex	1=male, 2=female
3.	pbs	number of hours spent watching PBS television per week
4.	math	ACT math score
5.	verbal	ACT verbal score

After importing the data into SPSS, use SPSS to answer each of the following questions:

1. Create a stem plot for the scores on the variable "pbs." (1a) Are there any outliers? If so, list the subject ID and score of each outlying data point. (1b) Cut and paste the stem plot from your SPSS output into the document you turn in for this assignment. Be sure to clearly label it #1b.

2. Create a stem plot for the scores on the variable "verbal." Are there any outliers? If so, list the subject ID and score of each outlying data point. Do not turn in the plot for this question.

3. Create a table of means comparing males and females scores on each of the three quantitative variables. Cut and paste this table into your homework that you turn in for this assignment. Be sure to clearly label it #3.

4. Are there any gender differences in ACT math or ACT verbal scores in this sample? Perform two t-tests to test the hypotheses that there are gender differences on each of these variables. Write one sentence for each stating your findings as you would in the Results section of a paper (do not cut and paste the information from the SPSS output). Do not forget to state the means being compared in each t-test, the degrees of freedom, the t score, and the p value or significance level.

5. Are there any gender differences in the number of hours of PBS watched per week? State the results of your t-test for this hypothesis as you did the t-tests in the previous question.

6. Do the results for #5 change if you eliminate the outliers (if any) from the data? If you identified any outliers in #1, replace those scores with missing values in the data window and re-run the analysis you performed for #5. State the results as you did for the previous t-tests.

7. Is there any relationship between ACT math and ACT verbal scores? In other words, are they correlated? Perform the appropriate analysis and state the results as you would in the Results section of a paper.

Reminder: For questions 2, 4, 5, 6, and 7 you should not be doing any cutting and pasting from the SPSS results window to your homework paper. You should be answering the questions in well-written sentences or paragraphs. All work must be typed - no handwritten work will be accepted.