[Limdep Nlogit List] Regarding calculating probabilities from ordered logit models

[Ganesh A R]

Dear Sir,

I am trying to manually calculate the probabilities from the estimated
coefficients of an ordered logit model.
I am currently using ordinal data with responses 0,1,2 and 3.
The LIMDEP manual says that if a constant "ONE" is included in the
specification, then the first threshold is considered to be zero. Hence
using that when I manually calculated the probability of each response, it
doesn't match with the probabilities that are calculated via the model
itself using the " ; prob = name  $" function.

Following is the method I used for calculating probabilities.

U = bo + b1x1 + b2x2 + ..... + bkxk
Where,
U = utility function
[b] = coefficients estimated from the model
[x] = explanatory variables

f(0) = 1 / (1 + exp(-U))
f(1) = 1  / (1 + exp(mu(1) - U)
f(2) = 1 / (1 + exp(mu(2) - U)
prob(0) =  f(0)
prob(1) = f(1) - f(0)
prob(2) = f(2) - f(1)
prob(3) = 1 - f(2)
where,
mu(1) and mu(2) are the threshold parameters obtained from the model
f(0), f(1) and f(2) is the CDF
prob(k) = probability of response k

Thanking you

Yours Sincerely

Ganesh Ambi Ramakrishnan

Doctoral Student