Basic Analysis and Graphing - SAS

212 Performing Contingency Analysis Chapter 6
Statistical Details for the Contingency Platform
For the purposes of this test, change size to an ordinal variable:
2. In the Columns panel, right-click on the icon next to size and select Ordinal.
3. Select Analyze > Fit Y by X.
4. Select sex and click Y, Response.
5. Select size and click X, Factor.
6. Click OK.
7. From the red triangle menu next to Contingency Analysis, select Cochran Armitage Trend Test.
Figure 6.21 Example of the Cochran Armitage Trend Test Report
The two-sided p-value (0.7094) is large. From this, you can conclude that there is no trend in the
proportion of male and females that purchase different sizes of cars.
Statistical Details for the Contingency Platform
This section contains statistical details for selected options and reports in the Contingency platform.
Statistical Details for the Agreement Statistic Option
Viewing the two response variables as two independent ratings of the n subjects, the Kappa coefficient
equals +1 when there is complete agreement of the raters. When the observed agreement exceeds chance
agreement, the Kappa coefficient is positive, with its magnitude reflecting the strength of agreement.
Although unusual in practice, Kappa is negative when the observed agreement is less than chance
agreement. The minimum value of Kappa is between -1 and 0, depending on the marginal proportions.
Quantities associated with the Kappa statistic are computed as follows:
P 0
– P e
κˆ = ---------------- where P and
1 – P = 0 p P ii
= e p p i. .i
e
i
i
The asymptotic variance of the simple kappa coefficient is estimated by the following:
var
A + B – C
= ------------------------ where , and
( 1 – P e
) 2 A = p ii
[ 1 – ( p i.
+ p .i
)( 1 – κˆ
)] 2 B ( 1 – κˆ
) 2 p ij
( p .i
+ p j.
) 2
=
n
i≠
j
i