What is Rate Comparison?

Risk indicator threshold type: Rate Comparison — performs a specialized statistical test to see if the current metric is significantly different from the overall study population. 

  1. Calculate post-rate — an estimate of the rate for the whole study: 

    (1+sum(events_k))/(1/ pre-rate+sum(times_k)), where events_k and times_k are numbers of events (for example, AEs) and time-units (for example, visits) for k-th study subdivision (for example, a site), and pre-rate is an initial estimate of the rate for the whole study.

  2. Calculate a confidence interval for the quantile of Poisson distribution of the number of events. The distribution parameters are the mean equal to post-rate * times (here "times" is the number of time-units) and the user-defined significance level "1-alpha". The meaning of the significance level is that the actual rate doesn't exceed the distribution's mean with the probability alpha if the comparison below is true.
  3. The number of events is compared with the lower boundary of the confidence interval if the direction of comparison is "lower" and with the higher boundary otherwise.
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