Example 28.5: Creating an Output Data Set Containing Chi-Square Statistics
This example uses the Color data from Example 28.1
to output the Pearson chi-square and the likelihood-ratio
chi-square statistics to a SAS data set. The following
statements create a two-way table of eye color versus hair
color.
proc freq data=Color order=data;
weight Count;
tables Eyes*Hair / chisq expected cellchi2 norow nocol;
output out=ChiSqData pchi lrchi n nmiss;
title 'Chi-Square Tests for 3 by 5 Table of Eye and Hair Color';
run;
proc print data=ChiSqData noobs;
title 'Chi-Square Statistics for Eye and Hair Color';
title2 'Output Data Set from the FREQ Procedure';
run;
The CHISQ option produces chi-square tests, the
EXPECTED option displays expected cell frequencies in the
table, and the CELLCHI2 option displays the cell
contribution to the chi-square. The NOROW and NOCOL options
suppress the display of row and column percents in the
table.
The OUTPUT statement creates the ChiSqData data set with
eight variables: the N option stores the number of
nonmissing observations, the NMISS option stores the
number of missing observations, and the PCHI and LRCHI options
store Pearson and likelihood-ratio chi-square statistics,
respectively, together with their degrees of freedom and
p-values.
The preceding statements produce Output 28.5.1 through
Output 28.5.2.
Output 28.5.1: Contingency Table
|
| Chi-Square Tests for 3 by 5 Table of Eye and Hair Color |
Frequency
Expected
Cell Chi-Square
Percent |
|
| Table of Eyes by Hair |
| Eyes(Eye Color |
Hair(Hair Color) |
Total |
| fair |
red |
medium |
dark |
black |
| blue |
69
66.425
0.0998
9.06 |
28
32.921
0.7357
3.67 |
68
63.22
0.3613
8.92 |
51
53.024
0.0772
6.69 |
6
6.4094
0.0262
0.79 |
222
29.13 |
| green |
69
59.543
1.5019
9.06 |
38
29.51
2.4422
4.99 |
55
56.671
0.0492
7.22 |
37
47.53
2.3329
4.86 |
0
5.7454
5.7454
0.00 |
199
26.12 |
| brown |
90
102.03
1.4187
11.81 |
47
50.568
0.2518
6.17 |
94
97.109
0.0995
12.34 |
94
81.446
1.935
12.34 |
16
9.8451
3.8478
2.10 |
341
44.75 |
| Total |
228
29.92 |
113
14.83 |
217
28.48 |
182
23.88 |
22
2.89 |
762
100.00 |
|
|
Output 28.5.2: Chi-Square Statistics
|
| Chi-Square Tests for 3 by 5 Table of Eye and Hair Color |
| Statistics for Table of Eyes by Hair |
| Statistic |
DF |
Value |
Prob |
| Chi-Square |
8 |
20.9248 |
0.0073 |
| Likelihood Ratio Chi-Square |
8 |
25.9733 |
0.0011 |
| Mantel-Haenszel Chi-Square |
1 |
3.7838 |
0.0518 |
| Phi Coefficient |
|
0.1657 |
|
| Contingency Coefficient |
|
0.1635 |
|
| Cramer's V |
|
0.1172 |
|
|
The contingency table in Output 28.5.1 displays eye and hair
color in the order in which they appear in the Color
data set. The Pearson chi-square statistic in Output 28.5.2
provides evidence of an association between eye and hair
color (p=0.0073).
The cell chi-square values show that most of
the association is due to more green-eyed children with fair
or red hair and fewer with dark or black hair. The
opposite occurs with the brown-eyed children.
Output 28.5.3: Output Data Set
|
| Chi-Square Statistics for Eye and Hair Color |
| Output Data Set from the FREQ Procedure |
| N |
NMISS |
_PCHI_ |
DF_PCHI |
P_PCHI |
_LRCHI_ |
DF_LRCHI |
P_LRCHI |
| 762 |
0 |
20.9248 |
8 |
.007349898 |
25.9733 |
8 |
.001061424 |
|
The OUT= data set is displayed in Output 28.5.3. It
contains one observation with the sample size, the number of
missing values, and the chi-square statistics and
corresponding degrees of freedom and p-values as in
Output 28.5.2.
Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.
