The results described below were observed in a hypothetical case-control study and reflect the "unbiased" results. You can assume that they reflect valid selection criteria for the study subjects, 100% participation by study subjects, no exposure misclassification, no biases, no confounding.

	Cases	Controls
Exposed	600	300
Unexposed	400	700

(a) Suppose the participation rate was only 90% among exposed cases, 75% among unexposed cases, and 70% among both exposed and unexposed controls. Fill in the observed 2x2 table below ):

	Cases	Controls
Exposed
Unexposed

(b) What is the observed odds ratio? (report with 2 decimals, )

(c) What kind of bias occurred in this scenario?