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Complete data cases
% distribution conditioning on
Stratum # A B C Count Percent
of total
A A & B A, C=0 A, C=1
1 0 0 0 400 33 53 67 80
2 0 0 1 200 17 27 33
100
75
3 0 1 0 100 8 13 67 20
4 0 1 1 50 4 7 33 25
100 100 100 100
5 1 0 0 240 20 53 62 83
6 1 0 1 150 13 33 38 88
100
7 1 1 0 40 3 9 67 17
8 1 1 1 20 2 4 33 12
100 100 100 100
Total 1,200 100
Missing value configurations
Configuration A B C Count
a. 0 0 . 12
b. 0 1 . 18
c. 1 0 . 10
d. 1 1 . 30
e. 0 . 0 40
f. 0 . 1 10
g. 1 . 0 15
h. 1 . 1 25
i. 0 . . 20
j. 1 . . 10
In this example, the eight strata in the cross-classification of the complete data cases are
numbered 1 through 8, and the percentages for each stratum are computed in four different ways:
unconditionally (i.e., the count as a percentage of all of the complete-data cases), conditionally based
on the value of A only, conditionally based on the value of A and B, and conditionally on the value
of A and C [the latter requires two columns for clarity]. Meanwhile, the 10 possible missing data
configurations are arrayed in the second table and labeled a. through j.
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www.sph.unc.edu/EPID168/ © Victor J. Schoenbach 16. Data management and data analysis - 543
rev. 9/27/1999, 10/22/1999, 10/28/1999