The importance of sample size for the estimation of F wave latency parameters in the peroneal nerve

We studied the peroneal nerve F waves in 20 healthy subjects and 20 patients with neuropathy to assess the effect of sample size on the accuracy of measurements of the following F wave latency parameters: F wave minimum latency, mean latency, median latency and F chronodispersion. The values obtained from a large sample (65-110 F responses) were compared with the corresponding values from smaller samples of 10, 20 and 40 responses. The results indicated that equally accurate measurements for all parameters were provided by larger F wave samples in patients, compared with healthy subjects. Amongst the various parameters, FchR required the largest and FL mean the smallest sample, in order to achieve results of the same accuracy. A sample of 40 fulfilled the requirements for all F wave latency parameters of the peroneal nerve in almost all subjects, a finding which is in good agreement with that of a similar study for the ulnar nerve.