the earlier slides we know that the exposure information in the hazard
period will be compared to the exposure information in the control data.
There are 2 types of control data we can use in a case crossover analysis.
The first type of data and also the most used is the exposure information
period”� which has the same length as the hazard period but at different
time point. For example, if the length of hazard period is 5 hours, the
control period is also a 5-hour period but it can be from the day before or
two days before.
- The second type of control data is the exposure information from the past,
it can be from the past month or past year. The analysis based on this type
of control data will be more complicated.