Do overactive bladder symptoms and their treatment-associated changes exhibit a normal distribution? Implications for analysis and reporting.

Dominant reporting of means implies the assumption of a normal distribution of overactive bladder syndrome symptoms but our data from two noninterventional studies do not support this assumption. We recommend that basal values and absolute symptom changes should be reported as medians and subjected to nonparametric analysis; means may be appropriate for the reporting of percentage changes of symptoms.