Assume that you are studying the effect of noise level on memory. Your study involves manipulating the level of noise while subjects try to memorize a list of words and then measuring the number of words the subjects correctly remember. For each statistical method listed below, 

(a) State the necessary or appropriate number of groups in the study, 

(b) State the necessary or appropriate measurement scale for the data, and 

(c) Draw a diagram of one possible design for the study:

A Pearson r

A t test

An F test

A χ² test