CHAPTER 17 More of a Good Thing: Multiple Regression 241

Taking a few steps with your software

The exact steps you take to run a multiple regression depend on your software, but

here’s the general approach:

1.

Assemble your data into a file with one row per participant and one

column for each variable you want in the model.

2.

Tell the software which variable is the outcome and which are the

predictors.

3.

Specify whatever optional output you want from the software, which

could include graphs, summaries of the residuals (observed minus

predicted outcome values), and other useful results.

4.

Execute the regression (run or submit the code).

Now, you should retrieve the output, and look for the optional output you

requested.

Interpreting the Output of a Multiple

Regression Analysis

The output from a multiple regression run is formatted like the output from the

straight-line regression described in Chapter 16.

Examining typical multiple

regression output

Figure 17-2 shows the output from a multiple regression analysis on the data in

Table 17-2, using R statistical software as described in Chapter 4. Other statistical

software produces similar output, but the results are arranged and formatted

differently.

Here we describe the components of the output in Figure 17-2:»

» ^{Code: The first line starting with Call: reflects back the code run to execute the}

regression, which contains the linear model using variable names: SBP ~

Age + Weight.