Biostats SPSS (The Effect of Weights)
vwccspt12
W10A_10.3_Step-by-StepGuide.docxWeek 11 Step by Step Application Guide 11.3
Effect of Weights
Problem 3. Logistic Regression with weights
a. Weight cases using the variable standwt (Standardized weight)
Step 1: Select Data View in SPSS Step 2: Click on the Scale icon in the menu bar
(Alternative: Data Weight cases)
Step 3: Select “Weight cases by”. Move standwt to Frequency variable. Click OK.
b. Use SPSS to rerun a logistic regression model with Q22a. “Have you ever looked online for -- Information about a specific disease or medical problem?” as your dependent variable, Sex as the independent variable, and Receduc as a covariate.
Repeat steps in 11.2a and 11.2b
SPSS output:
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Model Summary |
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Step |
-2 Log likelihood |
Cox & Snell R Square |
Nagelkerke R Square |
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1 |
2446.774a |
.128 |
.176 |
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a. Estimation terminated at iteration number 5 because parameter estimates changed by less than .001. |
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Variables in the Equation |
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B |
S.E. |
Wald |
df |
Sig. |
Exp(B) |
95% C.I.for EXP(B) |
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Lower |
Upper |
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Step 1a |
sex(1) |
-.767 |
.099 |
60.464 |
1 |
.000 |
.464 |
.383 |
.563 |
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|
receduc |
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|
156.855 |
3 |
.000 |
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receduc(1) |
-2.635 |
.382 |
47.584 |
1 |
.000 |
.072 |
.034 |
.152 |
|
|
receduc(2) |
-3.338 |
.384 |
75.383 |
1 |
.000 |
.036 |
.017 |
.075 |
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|
receduc(3) |
-3.708 |
.384 |
93.268 |
1 |
.000 |
.025 |
.012 |
.052 |
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Constant |
2.846 |
.379 |
56.393 |
1 |
.000 |
17.224 |
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a. Variable(s) entered on step 1: sex, receduc. |
Receduc(1)= HS grad; Receduc(2)=Some college; Receduc (3)=College+
c. How does weighting the cases change the outcome of the logistic regression?
Be sure to compare the OR and 95% CI for the un-weighted sample to the OR and 95% CI for the weighted sample State how this would effect your interpretation of the relationship of sex and education to the dependent variable
d. Discuss why it is important to weight cases from surveys with complex sampling schemes using the differing outcomes you have from parts 2 and 3 of this assignment.
