Hello,
I have survey data on timing to first birth for a group of women which
I think should be modelled within a competing risk framework. I know
if women have had a first birth, and if this birth occurred within a
marriage or outside of marriage. For now I am only interested in
doing a very basic descriptive analysis using a life table, rather
than multivariate analysis (I am aware of the add ons such as
stcompet).
I would like to see the distribution of failure (failure event=birth)
in total for all first births, and also separately for marital and
non-marital births.
The "age_ch1" variable is the age at which the first birth occurred.
The "birth" variable indicates if the woman had a birth or not by the
time of the survey. If she did not then her age_ch1 is given as her
age at the time of the survey ("age").
So the first thing I did was just:
ltable age_ch1 birth, failure
Then I wanted to see the failure rate for marital and non-marital
births. So I defined two new variables ("birth_s" and "birth_m"). The
first is equal to 1 if the woman had a non-marital birth, and 0
otherwise and the second is equal to 1 if the woman had a marital
birth and 0 otherwise. I believe this is how a competing risk life
table should be set up??
The two life tables are then
ltable age_ch1 birth_s, failure
ltable age_ch1 birth_m, failure
. list id age_ch1 birth birthstatus birth_s birth_m age in 1/20
+------------------------------------------------------------------------------+
| id age_ch1 birth births~s birth_s birth_m age |
|--------------------------------------------------------------------------------|
40. | 94 47 0 Censored 0 0 47 |
41. | 96 35 0 Censored 0 0 35 |
42. | 97 17 1 Other 1 0 42 |
43. | 98 20 1 Married 0 1 41 |
44. | 99 28 1 Married 0 1 41 |
|---------------------------------------------------------------------------------|
45. | 100 22 1 Married 0 1 55 |
46. | 101 23 1 Married 0 1 46 |
47. | 103 22 1 Married 0 1 45 |
48. | 105 27 0 Censored 0 0 27 |
49. | 106 27 1 Other 1 0 57 |
|------------------------------------------------------------------------------|
When I examine the cumulative failure rates they all look very
reasonable on their own. However, if I add up the two cumulative
probabilities for the marital and non-marital births, by age they do
not add up to the total cumulative probability of having a birth.
Should the cumulative probabilities of failure from the different
causes add up to the total cumulative failure? I can't understand what
I am doing wrong....
I hope this question makes sense
Any help would be greatly appreciated.
Cheers
Anna
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