people answer questions the way they think you want them answered
It is used when the experiment has only two treatment conditions; and subjects can be grouped into pairs
measuring the strength and direction of the relationship between two numerical variables
the effect of one variable on the response variable cannot be separated
the group that does not receive the experimental treatment
A cause and effect relationship in which one variable controls the changes in another variable
variable that is not among the explanatory or response variables in a study and yet may influence the interpretation of relationships among those variables.