All-
I ran a simple logistic regression in SAS to obtain the CIs on the regression coefficients. The CIs do not appear to be correct. Can anyone let me know what they think is going on. If you calculate the CIs by hand, these do not match what is provided in the SAS output.
Analysis of Maximum Likelihood Estimates | |||||
Parameter | DF | Estimate | Standard | Wald | Pr > ChiSq |
Intercept | 1 | 7.6653 | 22.9839 | 0.1112 | 0.7388 |
x | 1 | -1.1236 | 3.3681 | 0.1113 | 0.7387 |
Parameter Estimates and Wald Confidence | |||
Parameter | Estimate | 95% Confidence Limits | |
Intercept | 7.6653 | -37.3823 | 52.7128 |
x | -1.1236 | -7.7250 | 5.4779 |
By hand, I get the 95% (2-sided) CI for the intercept: (-52.71234 , 37.38174 )
SAS Code:
proc import datafile="C:\Users\BodnarJ\Desktop\functionalRequirement4_9_X\dataSim_FR_4_9_X.csv" dbms=csv out=work.anaDS replace;
delimiter="|";
getnames=yes;
guessingrows=7000;
run;
proc logistic data = anaDS ;
model yBinom1 = x / cl;
output out=propensity_scores pred=prob_flag;
run;
You must be modelling for the yBinom1=0 events. Try the syntax
model yBinom1(event='1') = x / cl;
Typically, the actual estimated coefficient for a logistic regression is approximately half-way between the upper confidence interval and the lower confidence interval.
Therefore, I conclude that your hand calculations are wrong.
You must be modelling for the yBinom1=0 events. Try the syntax
model yBinom1(event='1') = x / cl;
The above solution is absolutely correct!
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