258 PART 5 Looking for Relationships with Correlation and Regression

Seeing summary information

about the variables

At the top of Figure  18-4a, you can see information about the variables under

Descriptives. It can include means and standard deviations of predictors that are

numerical variables, and a count of how many individuals did or did not have the

outcome event. In Figure 18-4a, you can see that 15 of the 30 individuals lived and

15 died.

Assessing the adequacy of the model

In Figure 18-4a, the middle section starting with Deviance and ending with AIC

provides model fit information. These are measures that indicate how well the

fitted function represents the data, which is called goodness-of-fit. Some have test

statistics and an associated p value (see Chapter 3 for a refresher on p values),

while others produce metrics. Although there are different model fit statistics, you

will find that they usually agree on how well a model fits the data.

FIGURE 18-4:

Typical output

from a logistic

regression model.

The output on the

left (a) shows

statistical results

output for the

model, and the

output on

the right (b)

shows predicted

probabilities for

each individual

that can be

output as a

data set.

© John Wiley & Sons, Inc.