LaMont et al. tested for obstructive coronary artery disease (OCAD) among 113 me
ID: 3204081 • Letter: L
Question
LaMont et al. tested for obstructive coronary artery disease (OCAD) among 113 men
and 35 women who complained of chest pain or possible equivalent to their primary care
physician. Following Table shows the cross-classification of OCAD with gender. We wish to
use logistic regression analysis to determine how much greater the odds are of finding
OCAD among men than among women.
Table: Cases of Obstructive Coronary Artery Disease (OCAD) classified by sex
Disease
Males
Females
Total
OCAD present
92
15
107
OCAD not present
21
20
41
Total
113
35
148
Note: Use SPSS software to answer the question and give the interpretation
Disease
Males
Females
Total
OCAD present
92
15
107
OCAD not present
21
20
41
Total
113
35
148
Explanation / Answer
OCAD * Sex Crosstabulation
Sex
Total
male
female
OCAD
present
Count
92
15
107
% within OCAD
86.0%
14.0%
100.0%
% within Sex
81.4%
42.9%
72.3%
absent
Count
21
20
41
% within OCAD
51.2%
48.8%
100.0%
% within Sex
18.6%
57.1%
27.7%
Total
Count
113
35
148
% within OCAD
76.4%
23.6%
100.0%
% within Sex
100.0%
100.0%
100.0%
Model Summary
Step
-2 Log likelihood
Cox & Snell R Square
Nagelkerke R Square
1
156.314a
.117
.168
a. Estimation terminated at iteration number 4 because parameter estimates changed by less than .001.
Classification Tablea
Observed
Predicted
OCAD
Percentage Correct
present
absent
Step 1
OCAD
present
92
15
86.0
absent
21
20
48.8
Overall Percentage
75.7
a. The cut value is .500
Variables in the Equation
B
S.E.
Wald
df
Sig.
Exp(B)
95% C.I.for EXP(B)
Lower
Upper
Step 1a
Sex
1.765
.419
17.784
1
.000
5.841
2.572
13.266
Constant
-3.242
.592
29.981
1
.000
.039
a. Variable(s) entered on step 1: Sex.
Male population has 81.4% (92/113) OCAD and female 42.9% (15/35)
The final output suggest that Exp(B) = Odd ratio = 5.84, 95% CI, 2.5 to 13.2
It means that males have 5.8 times higher chance to develop OCAD as compared to females with 95% CI between 2.5 to 13.2
OCAD * Sex Crosstabulation
Sex
Total
male
female
OCAD
present
Count
92
15
107
% within OCAD
86.0%
14.0%
100.0%
% within Sex
81.4%
42.9%
72.3%
absent
Count
21
20
41
% within OCAD
51.2%
48.8%
100.0%
% within Sex
18.6%
57.1%
27.7%
Total
Count
113
35
148
% within OCAD
76.4%
23.6%
100.0%
% within Sex
100.0%
100.0%
100.0%
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