Computer Exercise: Paired t-test

Answer the following research question by running the appropriate t-test and writing up the results.

Suppose that you want to examine how psychotherapies such as cognitive behavioral therapy can relieve depression symptoms. You design a study and a group of older adults is invited to participate in a cognitive behavioral therapy intervention. At the beginning of the intervention, the PHQ-9* is given to assess older adults' depressive status ("Pre PHQ9"). At the end of the last intervention, the same PHQ-9 is administered ("Post PHQ9"). You formulate the following research question:

"Does the cognitive behavioral therapy intervention reduce the symptoms of depression?

*The PHQ-9 is a 9-item scale to assess individual's perceived depressive symptoms. The total score ranges from 0 to 27 (scores of 5-9 are classified as mild depression; 10-14 as moderate depression; 15-19 as moderately severe depression; 20 as severe depression).

Step 1.Open the attached dataset. You will use a different dataset called, PHQ study (not Book 5) for a paired t-test assignment. Use the entire dataset.

Step 2.Check the assumptions of the paired t-test. There are three assumptions:

• Only two measurements on the same person, or the same measure taken on a participant and a matched control subject are compared.
• Assumption of Normalityexamine normality of the two measures of the dependent variable (Pre PHQ9 and Post PHQ9, the variable names are "Pre_PHQ9" and "Post_PHQ9") and try data transformation if needed. Read the document,Test for normal distribution.
• The data are measured at the interval/ratio level.

Please note.Two PHQ variables are dependent because one participant is measured twice at two different time points. Therefore, theyshould bein a same unit of analysis. This means if you transform one PHQ9 variable, for example, Pre PHQ9, you should transform the other variable, Post PHQ9, to make two variables in a same unit of analysis.

Step 3.Run a paired t-test--you are comparing two dependent groups, Pre-PHQ9 group vs. Post-PHQ9 group and examine if there is a significant difference between the groups. Read or watchHow to run a paired t-test. CheckLearning SPSS or How to Video Echo360.

Step 4.Interpret SPSS outputs (Read the document,How to Interpret Paired t-test results in the Learning SPSSfolder in the left side menu column), and answer the question above and write up in Word document. In your paper, you should cite thevalue of test statistics, degrees of freedom (df), probability levels, and any other values necessary to determine what the results mean (e.g., group means and SDs).A sample answer to the question might be:

A paired t-test was conducted to compare the PHQ9 scores before and after the cognitive behavioral therapy intervention was given to older adults. There was a significant (or not significant depending on your p-value) increase (or decrease) in the PHQ9 scores after the intervention (mean=XXX, SD=XXXX) than before the intervention (mean=XXX, SD=XXXX); paired t(df)=XXX, p=XXXX. The results demonstrated the cognitive behavioral therapy intervention reduced the symptoms of depression for older adults. [This is one example: Please be creative. Just make sure your write-up includes t-value, df, p-value, and each group's mean and SD. Also do not forget to answer the assignment question in one or two sentences.]

Step 5.Make summary table. The following table template is an APA formatted table. Using a Word table tool, create own table. DO NOT copy/paste SPSS tables in your write-up (or any scholarly paper including your DNP project paper).

Pre- and Post-Intervention PHQ9 Score

	Mean	SD	Paired t	df	Significance (p)
Before intervention
After intervention

Step 6.Submit the followings. Please use Add Attachments.

• A text file in Word including a summary table
• SPSS output

Data Figures after inputing it calculator attached on image: