Chapter 8 Regression and Correlation 339correlated and which are not. One way of doing this is to create a correla-
tion matrix, in which the correlations (and associated p values) are laid out
in a square grid.
To illustrate the use of a correlation matrix, consider the Calculus work-
book. This fi le contains data collected to see how performance in a freshman
calculus class is related to various predictors (Edge and Friedberg, 1984).
Table 8-5 describes the variables in the Calculus workbook.Table 8-5 Calculus Workbook Variables
Range Name Range Description
Calc_HS A2:A81 Indicates whether calculus was taken in high school (0 5 no;
15 yes)
ACT_Math B2:B81 The student’s score on the ACT mathematics exam
Alg_Place C2:C81 The student’s score on the algebra placement exam given in
the fi rst week of classes
Alg2_Grade D2:D81 The student’s grade point in second-year high school algebra
HS_Rank E2:E81 The student’s percentile rank in high school
Gender F2:F81 The student’s gender
Gender_Code G2:G81 The student’s gender code (0 5 female; 1 5 male)
Calc H2:H81 The student’s grade in calculus
To open the Calculus workbook:1 Open the Calculus workbook from the Chapter08 data folder.
2 Save the workbook as Calculus Correlation Analysis to the same
folder. The workbook appears as shown in Figure 8-22.