The classic F-test for nonparallelism is widely used for bioassays with linear log dose-response lines to assess parallelism, or, more correctly, to examine the strength of evidence against a null hypothesis that the two lines are parallel. Alternative methods for assessing parallelism have been proposed, but their suitability for any particular case needs to be carefully considered. Here we examine some advantages and disadvantages of the different approaches. PRODUCT FOCUS: ALL BIOLOGICALSPROCESS FOCUS: QA/QCWHO SHOULD READ: QA/QC, ASSAY DEVELOPMENT, AND…