easy-to-use statistical software

The significance level, or P-value, is calculated using a general z-test (Altman, 1991):

where p is the observed proportion; p_{exp} is the Null hypothesis (or expected) proportion; and se(p) is the standard error of the expected proportion:

The P-value is the area of the normal distribution that falls outside ±z (see Values of the Normal distribution table).

MedCalc calculates the "exact" Clopper-Pearson confidence interval for the observed proportion.