Process capability - Negative Binomial

#1
Dear All,

I have attribute that show overdispersion and seem to be distributed according to a negative binomial distribution.

I have the following questions:

1. How can I check in Minitab if my data is distributed according to Negative Binomial? (I used Crystal Ball for this specific case)

2. How do I calculate the process capability in Minitab in such case? Minitab tells me that data is overdispersed and suggests to use the Laney U' chart but it keeps calculating the chance to have zero defects as Exp(-dpu) which is valid for Poisson. Any suggestion?

Thank you
 

rogojel

TS Contributor
#2
hi,
as far as I know Minitab does not handle the negative binomial. If you identified the distribution ( meaning you know the estimates of the parameters) you could just use Crystal Ball or any other simulation SW to estimate the proability of having a defect, which is the dpmo/10^6 .
regards