Alpha Errors, Beta Errors and Negative Trials

Reports of negative trials arc increasing in number as standard therapyfor many gastrointestinal diseases is refined. The validity of a negative report dependson the number of patients in the trial, the alpha and bern error and the difference inefficacy which the trial is able to detect. The relationship between these parametersis discussed and a formula given for the calculation of trial size. All reports of negativetrials should include not only the number of patients involved and the level ofsignificance of the results but also the beta error and the detectable difference inefficacy of the treatments