The power of statistical tests in science teachnig research

A calculation of the probability of rejecting H 0 when it should be rejected (power) was completed on each of the 66 applicable articles in Volumes 6 and 7 (1969, 1970) of the Journal of Research in Science Teaching. These power calculations utilized the effect size definitions and tables developed by Cohen (1969). The mean power of each article to detect small, medium, and large effect sizes was determined from its major statistical tests. These mean powers were then compiled and analyzed. The powers calculated for the different effect sizes were disturbingly low (small, 0.22; medium, 0.71; large, 0.87) but not generally as low as Cohen (1962) found in an analysis of another behavioral journal. Recommendations for improving confidence in research in science teaching is provided and centers on significant increases in sample sizes and an understanding of power and its relation to a, effect size and sample size.