Modeling and Multivariate Methods - SAS

454 Correlations and Multivariate Techniques Chapter 17
Computations and Statistical Details
You can use Cronbach’s α to evaluate the agreement in the perceived way the groups ranked the items. Note
that in this type of example, where the values are the same set of ranks for each group, standardizing the data
has no effect.
1. Open Danger.jmp from the Sample Data folder.
2. Select Analyze > Multivariate Methods > Multivariate.
3. Select all the columns except for Activity and click Y, Columns.
4. Click OK.
5. From the red triangle menu for Multivariate, select Item Reliability > Cronbach’s α.
6. (Optional) From the red triangle menu for Multivariate, select Scatterplot Matrix to hide that plot.
Figure 17.5 Cronbach’s α Report
The Cronbach’s α results in Figure 17.5 show an overall α of 0.8666, which indicates a high correlation of
the ranked values among the three groups. Further, when you remove the experts from the analysis, the
Nonstudents and Students ranked the dangers nearly the same, with Cronbach’s α scores of 0.7785 and
0.7448, respectively.
Computations and Statistical Details
Estimation Methods
Robust
This method essentially ignores any outlying values by substantially down-weighting them. A sequence of
iteratively reweighted fits of the data is done using the weight:
w i = 1.0 if Q < K and w i = K/Q otherwise,