Thanks for your help!

- Thread starter MRH
- Start date

Thanks for your help!

thanks for your help! Here is my code:

. logistic earlydea TreamentArm ElevatedPulse Leucytosis Hypotensive MeanO2Sat

> Age3group, vce(bootstrap, reps(1000))

(running logistic on estimation sample)

Bootstrap replications (1000)

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Logistic regression Number of obs = 932

Replications = 1000

Wald chi2(6) = 44.78

Prob > chi2 = 0.0000

Log likelihood = -115.92168 Pseudo R2 = 0.2552

------------------------------------------------------------------------------

| Observed Bootstrap Normal-based

earlydea | Odds Ratio Std. Err. z P>|z| [95% Conf. Interval]

-------------+----------------------------------------------------------------

TreamentArm | 3.144032 1.304644 2.76 0.006 1.394034 7.090889

ElevatedPu~e | 3.786335 1.752647 2.88 0.004 1.5283 9.380576

Leucytosis | 5.702793 2.418744 4.10 0.000 2.483503 13.09515

Hypotensive | 3.434464 1.722635 2.46 0.014 1.285047 9.179073

MeanO2Sat | 1.880585 .266983 4.45 0.000 1.423801 2.483913

Age3group | 1.324033 .5473046 0.68 0.497 .5889042 2.976823

------------------------------------------------------------------------------

. estat gof

no observations

r(2000);

. lroc

no observations

r(2000);

Well, everything seems fine, this should be working

Have you tried reducing the replicates? I was thinking that, since you have very few positive outcomes, at some point the replication process will sample only 0's. I really don't know how STATA handles this cases, so this could be a problem. Some literature claims that 200 or 300 replicates could be good enough to estimate this type of variances.

The other alternative I can think of is using the prefix bootstrap:. This is usually not recommended, since the option vce(bootstrap) may be a better alternative, but in your case, you could try it to see if it can solve this problem.

Don't you have missing data or something that may be causing troubles in your dataset? Haven't you subset the data? I assume your dependent variable is correctly coded as 0 and 1, isn't it? Other than that I'm blank.