Statistics for People Who (Think They) Hate Statistics

by Neil J. Salkind

The entire curve represents all the possible outcomes based on a specific null hypothesis, such as the difference between two groups or the significance of a correlation coefficient. The critical value is the point beyond which the obtained outcomes are judged to be so rare that the conclusion is that the obtained outcome is not due to chance but to some other factor. In this example, we define rare as having a less than 5% chance of occurring. If the outcome representing the obtained value falls to the left of the critical value (it is less extreme), the conclusion is that the null hypothesis is the most attractive explanation for any differences that are observed. In other words, the obtained value falls in the region (95% of the area under the curve) where we expect most outcomes to occur if the null hypothesis is true.