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We can now write the multiple regression equation for these data:
Y ¼ 1 : 5363 þ 0 : 0006 X 1 þ 0 : 0003 X 2 þ 0 : 0021 X 3
7.3 Using the Regression Equation to Predict FROSH GPA
Objective:
To find the predicted FROSH GPA using an SAT Reading Score of
600, an SAT Writing Score of 500, and an SAT Math Score of 550
Plugging these three numbers into our regression equation gives us:
Y ¼ 1 : 5363 þ 0 : 0006 60 ðÞþ 0 : 0003 50 ðÞþ 0 : 0021 55 ðÞ
Y ¼ 1 : 5363 þ 0 : 36 þ 0 : 15 þ 1 : 155
Y ¼ 3 : 20
ð
since GPA scores are typically measured in two decimals
Þ
If you want to learn more about the theory behind multiple regression, see
Keller ( 2009 ) and Gould and Gould ( 2002 ).
7.4 Using Excel to Create a Correlation Matrix in Multiple
Regression
The final step in multiple regression is to find the correlation between all of the
variables that appear in the regression equation.
In our example, this means that we need to find the correlation between each of
the six pairs of variables:
To do this, we need to use Excel to create a ‘‘correlation matrix.’’ This matrix
summarizes the correlations between all of the variables in the problem.
Objective:
To use Excel to create a correlation matrix between the four variables
in this example
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