Note on Statistical Differences
UNTIL THE past two decades the reliability of statistical values was determined by the use of the numerical values assigned to properties of the nor mal probability curve. More recently the reliabili ty of differences, as well as other statistics, is cal culated with chi-square and variance ratio. The method, however sound, is very frequently misinter preted; for example, in many of the research stud ies the conclusion is that there was no difference be tween the control and the experimental groups at the 1 percent level, 2 percent level, or 5 percent level, etc. A fairly common interpretation is that there is no difference between the two groups. As a matter of fact, what is usually intended is that there were not sufficient cases to result in an obtained difference beyond the probability of being attributable to chance errors of sampling and measurement in one chance in 100, two chances in 100, or five chances in 10 0. In other words, the real conclusion in a great many of these studies is that the investigation did not em ploy enough cases to permit a statistically reliable difference to be concluded.