Cochran formula for sample size determination online dating
To deal with this, we could stratify by age at 5 year intervals.
When the data was pooled, it appeared that the risk ratio for the association between obesity and CVD was 1.79.
Successful statistical practice is based on focused problem definition.
In sampling, this includes defining the population from which our sample is drawn.
The adjustment for age produces estimates of the relative risk and odds ratio that are much closer to the stratum-specific estimates (the adjusted estimates are weighted averages of the stratum-specific estimates).
Note that there is also an Cochran-Mantel-Haenszel equation which can be used when dealing with incidence rates in prospective studies in which incidence rates are computed.