analysis if the control data were the exposure information over the past:
The first step is to get the concurrence observed odds of the exposure
during the hazard period. Remember that the odds of event A is the
probability of having event A divided by the probability of not having event
A. In the analysis,instead of using division, we will represent the odds as
(m:n). Thus the odds of the exposure during the hazard period for an
individual who had the exposure should be (1:0), and the odds for an
individual not having exposure during hazard period should be (0:1).