I run a multinomial logistic regression model, where the outcome variable has three levels. From this I can obtain predicted probabilities for each level of the outcome. I would like to put confidence intervals around these probabilities, but I am not sure how to do it. I can obtain confidence intervals for the linear prediction (using the -stdp- option with -predict-), but I am not sure how to incorporate this information into the equations which relate the linear prediction to the probability:
P(y=1) = 1/(1+exp(beta2*x)+exp(beta3*x))
P(y=2) = exp(beta2*x)/(1+exp(beta2*x)+exp(beta3*x))
P(y=3) = exp(beta3*x)/(1+exp(beta2*x)+exp(beta3*x))
(where beta2*x is the linear prediction for outcome level 2, etc)
I apologise if this is more of a stats question than specifically a Stata issue.
Thanks in advance.
Dan
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Daniel Dedman
Public Health Information Specialist/Analyst
North West Public Health Observatory
t: 0151 231 4552
m: 07812 192578
f: 0151 231 4515
e: [email protected]
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