The participant-observer: a source of invalidity in measuring motor skills?

Test validity can be defined as the accuracy of a test score. Artifacts, sources of error that affect validity, have been studied in both research design and written test frameworks but have received little attention in the context of tests of motor behavior in an educational setting. One potential source of invalidity in motor skill testing is the presence of participant-observers. The participant-observer effect is defined as the influence of the presence of other subjects who are waiting to be tested or who have already been tested on subjects who are being tested. This study was designed to measure the test performances of 175 college women with participant-observers present and with participant-observers absent. The test was an overarm throw for speed measured by an incident light velocimeter. The data were analyzed using 2 X 4 fixed-effects analysis of variance. The presence of other participant-observers did not elicit performance scores that were different from those of subjects tested alone. Thus testing subjects in groups where one member of the group is tested while the others observe did not adversely affect performance on the overarm throw compared with that of subjects tested alone.