308 PART 6 Analyzing Survival Data

Next, count how many participants experienced the event during each slice, and

how many were censored, meaning they were last observed during this time slice

and had not experienced the event. From Figure 21-2, you see that»

» ^{During the first year after surgery, one participant died (#1), and one partici-}

pant was censored (#5, who was LFU).»

» ^{During the second year, no participants died or were censored.»}

» ^{During the third year, two participants died (#4 and #9), and none were}

censored.

Continue tabulating deaths and censored times for the fourth through seventh

years, and enter these counts into the appropriate cells of a spreadsheet like the

one shown in Figure 21-3.

To fill in the table shown in Figure 21-3:»

» ^{Put the description of the time interval that defines each slice into Column A.»}

» ^{Enter the total number of participants alive at the start into Column B in the}

0–1 yr row.»

» ^{Enter the counts of participants who died within each time slice into Column C}

(labeled Died).»

» ^{Enter the counts of participants who were censored during each time slice}

into Column D (labeled Last Seen Alive).

After you’ve entered all the counts, the spreadsheet will look like Figure  21-3.

Then you perform the calculations shown in the Formula row at the top of the

figure to generate the numbers in all the other cells of the table. (To see what it

looks like when the table is completely filled in, take a sneak peek at

Figure 21-4.)

FIGURE 21-3:

A partially

completed life

table to analyze

the survival times

shown in

Figure 21-2.

© John Wiley & Sons, Inc.