Part IV discussed the use of statistics to describe scores on variables and to identify the strength and direction of relationships between variables. Statistics applied in this way help describe characteristics of cases studied in research. In terms of the research model introduced in chapter 2, statistics used this way help establish empirical relationships linking scores on independent and dependent variables.
But chapter 2 also pointed out that statistics are used to help make two types of inference. Statistical inference uses probability theory to draw conclusions that transcend the relationships between variables per se. One of these involves inferences about whether an observed