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eldad_galili
Level III

how to the find the logistic variability parameter

Hello everybody,

 

I am performing analysis for OK/NOK output, see attached files.

I need to find the estimate of gamma, the logistic variability parameter. Where can I find it in the analysis report?

 

Thank you very much.

 

Test.JPG

1 REPLY 1
peng_liu
Staff

Re: how to the find the logistic variability parameter

Do you mean the scale parameter in a logistic distribution? If so, you won't be able to find it in a logistic regression report. Logistic regression is usually formulated to address the relationship between probability and explanatory variables:

peng_liu_1-1607533602570.png

The simplest case will be just one explanatory variable, so the above form reduces to this:

peng_liu_3-1607533835951.png

Meanwhile, the logistic distribution function looks like the following, in which s is the scale parameter:

peng_liu_5-1607534071767.png

Compare this equation with the one above it, you should be able to back out parameter m and s from beta0 and beta1. I.e. 1/s  = beta1 and -m/s = beta0.

However, you won't be able to find m and s even in the simplest logistic regression report, because they don't have appropriate interpretations in the logistic regression context, in which beta's can explain changes in log-odds while changing explanatory variables.