Outlier detection in collaborative studies.

Extended tables of critical values for the reduction in standard deviation tests for single and paired outliers recommended for collaborative studies are presented. Critical values for the single outlier test are derived mathematically and those for the paired test are derived from computer simulations. The single outlier test becomes more and more stringent as the size of the study increases. A confidence interval approach is suggested as a means to treat all sizes of collaborative studies in a uniform manner.