To determine characteristics associated with Y = whether a cancer patient achieved remission (1 = yes), a study used logistic regression. The most important explanatory variable was a labeling index (LI) that measures proliferative activity of cells after a patient receives an injection of tritiated thymidine. It represents the percentage of cells that are “labeled.” Table 4.8 shows the grouped data. Software reports Table 4.9 for a logistic regression model using LI to predict π = P (Y = 1). A. Show how software obtained π ̂ = 0.068 when LI = 8. B. Show that π ̂ = 0.50 when LI = 26.0 D. The lower quartile and upper quartile for LI are 14 and 28. Show that π ̂ increases by 0.42, from 0.15 to 0.57, between those values. E. When LI increases by 1, show the estimated odds of remission multiply by 1.16

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To determine characteristics associated with Y = whether a cancer patient achieved remission (1 = yes), a study used logistic regression. The most important explanatory variable was a labeling index (LI) that measures proliferative activity of cells after a patient receives an injection of tritiated thymidine. It represents the percentage of cells that are “labeled.” Table 4.8 shows the grouped data. Software reports Table 4.9 for a logistic regression model using LI to predict π = P (Y = 1). A. Show how software obtained π ̂ = 0.068 when LI = 8. B. Show that π ̂ = 0.50 when LI = 26.0 D. The lower quartile and upper quartile for LI are 14 and 28. Show that π ̂ increases by 0.42, from 0.15 to 0.57, between those values. E. When LI increases by 1, show the estimated odds of remission multiply by 1.16
Table 4.8. Data for Exercise 4.1 on Cancer Remission
Number of Number of
Number of Number of
Cases Remissions
Cases
LI
8
2
18
1
10
2
20
3
12
3
22
2
14
3
24
1
16
3
26
1
Source: Reprinted with permission from E. T. Lee, Computer Prog. Biomed., 4: 80-92, 1974.
Table 4.9. Computer Output for Problem 4.1
Standard
Error
li
Parameter Estimate
Intercept -3.7771
0.1449
Obs
72
1
Remissions LI
2
li
8
10
0
0
0
0
0
Source
li
1.3786
0.0593
DF
1
remiss
0
0
1
2
1
0
1
n
2
2
LI
28
32
34
38
LR Statistic
Chi-Square
8.30
Number of Number of
Cases Remissions
1
1
1
3
Likelihood Ratio
95% Conf. Limits
pi_hat
0.06797
0.08879
-6.9946 -1.4097
0.0425 0.2846
Pr > ChiSq
0.0040
lower
0.01121
0.01809
1
0
1
2
Chi-Square
7.51
5.96
upper
0.31925
0.34010
Transcribed Image Text:Table 4.8. Data for Exercise 4.1 on Cancer Remission Number of Number of Number of Number of Cases Remissions Cases LI 8 2 18 1 10 2 20 3 12 3 22 2 14 3 24 1 16 3 26 1 Source: Reprinted with permission from E. T. Lee, Computer Prog. Biomed., 4: 80-92, 1974. Table 4.9. Computer Output for Problem 4.1 Standard Error li Parameter Estimate Intercept -3.7771 0.1449 Obs 72 1 Remissions LI 2 li 8 10 0 0 0 0 0 Source li 1.3786 0.0593 DF 1 remiss 0 0 1 2 1 0 1 n 2 2 LI 28 32 34 38 LR Statistic Chi-Square 8.30 Number of Number of Cases Remissions 1 1 1 3 Likelihood Ratio 95% Conf. Limits pi_hat 0.06797 0.08879 -6.9946 -1.4097 0.0425 0.2846 Pr > ChiSq 0.0040 lower 0.01121 0.01809 1 0 1 2 Chi-Square 7.51 5.96 upper 0.31925 0.34010
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