ABSTRACT
This chapter presents a more general discussion of how to characterize the relationship among variables. Creating a scatterplot or calculating a correlation coefficient can be suggestive of a positive, negative, or zero relationship between two variables. In quantitative research, external validity is about whether our conclusions, based upon the observations in our sample, are true for the larger population from which we drew the sample. The principle of constructing a confidence interval applies to many situations where we are interested in estimating a parameter. The confidence interval provides a measure of the reliability of an estimate of the relationship among variables. Continuous variables are ones that can take on essentially any value over the range of values they are possible to take.
