Progress Check

Use this activity to assess whether you and your peers can:

• Create a contingency table in StatCrunch.
• Use conditional percentages to analyze the data in a contingency table.
• Draw conclusions based on the analysis of the data in a contingency table.

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 (no 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 already done so, open the depression data set in the Stats at Cuyamaca College group on StatCrunch (directions - opens in a new tab).

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) To include a meaningful table with your response, complete each of the following.
   • Copy the table in your StatCrunch output window and paste it into the textbox. (directions)
   • After you paste the content of the your StatCrunch output window into the textbox, keep the table titled Contingency table results: and delete the Chi-Square results: table.
   • Make your contingency table more meaningful to the reader. Use the theTreat andOutcome variable descriptions (provided above in the Variables section) to replace the numeric row labels and the numeric column labels with meaningful words. How do we replace the row and column labels? After you copy and paste the contingency table into your response, click in an appropriate table cell, delete the numeric label, and type the appropriate "word" label.
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.