Failure Rate

An accessibility metric introduced by Sullivan and Matson (2000) that, for a given page and a given checkpoint, divides the number of checkpoint violations found by the maximum number of violations that could have occurred on that page. Failure Rate produces a normalised value between 0 and 1, where 0 indicates perfect conformance on that checkpoint and higher values indicate worse accessibility. It is simple to compute and interpret, but depends entirely on the accuracy of the underlying automated check and reflects conformance rather than severity of user impact.