ASM Practice Exam 4 #11

[jensen]

Given 1000 lives at age 20.

Ages; deaths; Censored
21; 2; 12
22; 3;13
23; 4; 14
24; 5; 15

Deaths adn censoring occur at exact.

Calculate Kaplan Meier est of 2q21.

Is this right?
2q21 = death by age 22 or 23
= 1 - 2p21
= 1 - p21*p22

How come no details for deaths and censored at age 20 is needed for the calculation?

Thanks a bunch.

[adisah]

yes thats correct,i had 1-p21p22=1-998/1000*995/998=0.005

[jensen]

the answer is 0.007. But the question gave us the risk set at age 20, without any details on deaths and lives censorerd at age 20. Is it because it's irrelevant?

[Gandalf]

"Deaths and censoring occur at exact." What does that mean? Maybe the deaths at 21 are assigned to the risk year from 20 to 21, so your numerator is based on the 3 deaths at 22 and the 4 deaths at 23, which might well give an answer of .007 (I didn't plug in the censoring info, which might raise it to .008 under that interpretation).

[Abraham Weishaus]

It's a little higher than 0.007 (Jensen rounded the answer). Exact age means right on the birthday. What happens at exact age 20 is not relevant; the 1000 lives who are 20 didn't die or leave instantaneously, or at least we generally don't assume that.