In this activity, you will investigate the first question related to the study described below.

Some features of this activity may not work well on a cell phone or tablet. We highly recommend that you complete this activity on a computer.

Here are the directions and grading rubric for the Learn by Doing discussion board exercises.

A list of StatCrunch directions is provided at the bottom of this page.

Context

Clinical depression is a recurrent illness requiring treatment and often hospitalization. Nearly 50% of people who have an episode of major depression will have a recurrence within 2-3 years. Being able to prevent the recurrence of depression in people who are at risk for the disease would go a long way to alleviate the pain and suffering of patients.

During the 1980’s the federal government, through the National Institutes of Health (NIH), sponsored a large clinical trial to evaluate two drugs for depression. There were 3 treatment groups. Patients received either Imipramine (Imip), Lithium (Li), or a Placebo (Pl). Researchers randomly assigned patients to one of the 3 treatment groups and followed them for 2-4 years to track any recurrences of depression.
(Prien et al., Archives of General Psychiatry, 1984).

Variables

· Hospt: Which hospital the patient was from: Labeled 1, 2, 3, 5 or 6

· Treat: 0=Lithium; 1=Imipramine; 2=Placebo

· Outcome: 0=Success 1=Failure (recurrence of depression)

· Time: Number of weeks until a recurrence (if outcome=1) or until study ended (if outcome=0)

· AcuteT: How long the patient was depressed before the start of the current study, measured in days

· Age: Age in years

· Gender: 1=Female 2=Male

Data

If you have not done so already, download the depression datafile (as always, if a login box opens, just close it and then download the file). Then upload the file in StatCrunch.

Prompt

We will analyze the data to answer the 1st research question: Which of the drugs (if either) was more successful in preventing the recurrence of depression relative to the placebo?

In the previous lab-preparation activity, we determined that we will analyze the data using a two-way table and conditional percentages.

1. Use StatCrunch to produce a two-way contingency table. (directions)
   Copy the table in your StatCrunch output window and paste it in your initial discussion post. (directions)
   After you paste the content of your StatCrunch output window into your discussion post, keep the table titled Contingency table results: and delete the Chi-Square results: table.
2. Analyze the data in your two-way table by finding appropriate conditional percentages. Write each conditional percentage as a ratio (e.g. 25 out of 40) and as a percentage (e.g. 25/40 = 62.5%). Then write a sentence that explains the meaning of the percentage in the context of the research question.
3. Draw a conclusion. Based on this study, which drug was the most effective in preventing the recurrence of depression? Support your conclusion using conditional percentages.