Reference no: EM133920258

Question

In the same case-control study looking at risk factors for ovarian cancer, the investigators also wanted to examine whether parity (the number of times a woman has given birth after 24 weeks of gestation) was associated with ovarian cancer. Among the 391 cases and 640 controls, 311 cases and 543 controls had at least one child.

1. What is the OR of ovarian cancer associated with having at least one child compared with having no children? Please describe the observed association in a sentence.

2. When recruiting women into this study, 203 women diagnosed with ovarian cancer who were approached and asked to participate did not respond. In the case population in this study, it was common for women diagnosed with ovarian cancer to move in with relatives, including their children, during treatment. Suppose that among those 203 women with ovarian cancer, 65% were living with children who encouraged them to join the study and, and those women finally got tired of their children telling them what to do, and they agreed to be in the study after all. What would the observed OR be after these women joined the study?

3. What kind of bias would be introduced due to the circumstances described in 3b?

4. In one or two sentences, please describe the type and direction of the bias in 3b, and the biased result compared with the "true" association.