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Introduction to Categorical Data Analysis

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PROBLEMS 235<br />

7.5 Refer <strong>to</strong> Table 2.10 on death penalty verdicts. Let D = defendant’s race, V =<br />

victim’s race, and P = death penalty verdict. Table 7.20 shows output for<br />

fitting model (DV, DP, PV ). Estimates equal 0 at the second category for<br />

any variable.<br />

a. Report the estimated conditional odds ratio between D and P at each level<br />

of V . Interpret.<br />

b. The marginal odds ratio between D and P is 1.45. Contrast this odds ratio<br />

with that in (a), and remark on how Simpson’s paradox occurs for these<br />

data.<br />

c. Test the goodness of fit of this model. Interpret.<br />

d. Specify the corresponding logistic model with P as the response.<br />

Table 7.20. Computer Output for Problem 7.5 on Death Penalty<br />

Criteria For Assessing Goodness Of Fit<br />

Criterion DF Value<br />

Deviance 1 0.3798<br />

Pearson Chi-Square 1 0.1978<br />

Standard LR 95% Confidence<br />

Parameter DF Estimate Error Limits<br />

Intercept 1 3.9668 0.1374 3.6850 4.2245<br />

v black 1 −5.6696 0.6459 −7.0608 −4.4854<br />

d black 1 −1.5525 0.3262 −2.2399 −0.9504<br />

p no 1 2.0595 0.1458 1.7836 2.3565<br />

v*d black black 1 4.5950 0.3135 4.0080 5.2421<br />

v*p black no 1 2.4044 0.6006 1.3068 3.7175<br />

d*p black no 1 −0.8678 0.3671 −1.5633 −0.1140<br />

LR Statistics<br />

Source DF Chi-Square Pr > ChiSq<br />

v*d 1 384.05

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