the simple binomial test to the event study,
which indicates whether the cross-sectional frequency of positive abnormal
returns is significantly different from 0.5. This test is stable
to outliers, in other words allows for checking if the result is driven by
few companies with extremely large abnormal performance. For this test the
estimation period and the event period must not overlap, otherwise an error
will be thrown. The test statistic is assumed to have a normal distribution
in approximation under a 