A hypothesis is a tentative statement about empirical reality, involving a relationship between two or more variables. A dependent variable is a variable that is hypothesized to vary depending on or under the influence of another variable. Crime rates vary by urbanization. When we find a relationship between two variables this is known as an association or correlation. Associations can be positive or negative.
Positive associations exist when one variable increases as the other variable increases.
Negative associations exist when one variable increases as the other variable decreases in value. Again, see Exhibit 2.5 for examples.