ABSTRACT
To establish the criterion validity of a measurement, we will use statistics. The most basic statistics are the descriptive statistics of mean, median, and mode. In describing a group of scores, we may find it to be a normal (standard) distribution. The standard distribution is very useful, because for this shape distribution, the percentage of data encompassed by each standard deviation is predictable. This allows us to make predictions and recognize data that is unusual. We will use inferential statistics to evaluate criterion validity, but we will start with basic statistics.
