Chapter 12: Principles of Test Selection and Administration-Reliability of tests

      In our last post we went over the validity of athletic testing. Today we will go over the reliability of athletic testing. These terms go hand in hand with athletic testing. You can't have one without the other. Think of that friend that is always reliable. The one where you ask for something and you get it in a timely fashion. That is the reliability in terms of athletic testing. You want the degree of consistency and repeatability. We are looking at the repeatability of the test-not the results. A 40-yard dash is reliable for it measures speed time and time again. It is a consistent, reliable test. The NFL Combine is famous for the 40 times (especially the skill guys). Over time scores are fairly consistent (just faster). Since those scores are lumped together, we know that a 40-yard dash has test-retest reliability. If you were to take scores from the past five years of the fastest sprinters and lay them out the difference in those scores is the typical error of measurement (TE). TE often comes from the biological variation of various athletes. 

    In terms of variation of the reliability of tests a few things can be contributed. 

    Intrasubject variability

    Intrasubject is the lack of consistent performance by the person being tested. Simple, and clear cut. It happens within sports. Injured during the offseason, preparation could be off, could be anything, it happens.

Interrater reliability

    Interrater reliability can also be referred to as objectivity or interrater agreement. This is the degree to which different raters agree in test results. This alludes to the leniency of different graders. On the 40-yard dash example does one rater use electronic timer as opposed to a stopwatch? Or in a 1RM squat example how does one rater judge squat depth? Another example is gymnastics- graders are subjective in their scores.   

Intrarater variability

    Intrarater variability is the lack of consist scores from a tester. If interrater pertains to individual graders than intrarater is from the overall grader or who is in charge of the test. A coach may want to see improvement amongst athletes and be stricter on the beginning test and lenient on the posttest. Another could be attributed towards inattentiveness, lack of concentration or a failure to follow the standardization of a test.