Part 2. Conducting t-tests

In the case-control study by Cho et al, demographic factors were compared between cases and controls. Continuous factors, such as age and total caloric intake, were compared between cases and controls using two-sample 2-sided t-tests. Use the data presented in Table 1 to answer the following questions:

1. Given the values in Table 1, use an appropriate test to determine if the total caloric intake for cases differs from 2000 kcal/day. Remember to state your hypotheses, assumptions, test statistic, and results.

2. Calculate the 95% CI's of total caloric intake separately for the cases and controls. What can be concluded about the statistical similarities of the two population means?

3. Calculate the 95% CI of the difference of total caloric intake means between cases and controls. Provide an interpretation of the results. What can be concluded from this?

4. Use an appropriate test to determine whether there is a significant difference in total caloric intake between cases and controls. Be sure to clearly state your hypotheses, test statistic, and appropriate conclusions.

5. Pretend that cases act as their own control in this study (ie data were collected prior to colorectal cancer was diagnosed and then after diagnosis). What type of test would you conduct to determine if total caloric intake was different between cases and controls? How would this test differ from your previously conducted test?