During the past 30 years many pediatric assessment and outcome measures have been developed. Based on Rasch analysis, the Pediatric Evaluation of Disability Inventory (PEDI) was designed to measure functional status by asking parents about both the skills of their children and the performance of daily tasks in three functionally important domains…

This commentary on EC 608 301 points out that devotion to the natural science canon of experimental proof in the area of generality testing requires proof procedures that are difficult, expensive, or impossible, but adopting a different canon of proof will not produce the desired certainty about the accuracy of the answer. (JDD)