Stata Version: Stata/MP 15.1

Operating System: Windows 7 Enterprise (SP1)

Hi Statalist members,

I am trying to build a zero-truncated negative binomial regression model, but am having difficulties interpreting the results. I am not experienced with this type of modelling, and have followed an online tutorial in building my model. However, the result I am getting is not making sense to me. Here is my problem:

My outcome variable is number of visits by a patient to a clinic in a year (count variable starting from 1; range 1-66, mean 4.2, SD 4.7, Var 22.5 Sk 4.6, Kur 37.8)

My co-variates are age (continuous from 0 to 100), gender (binary), and size of clinic (categorical; 4 categories)

The syntax I use is
followed by
to obtain estimates.

The model output is as follows:

and the estimate output is as follows:

0.75 visits per patient in a year for males ( or 0.9 for females) doesn't make sense when the lowest number of visits is 1. Why am I getting less than 1? Is there a step that I am missing (changing distribution, etc.) , or am I doing something completely wrong?

Operating System: Windows 7 Enterprise (SP1)

Hi Statalist members,

I am trying to build a zero-truncated negative binomial regression model, but am having difficulties interpreting the results. I am not experienced with this type of modelling, and have followed an online tutorial in building my model. However, the result I am getting is not making sense to me. Here is my problem:

My outcome variable is number of visits by a patient to a clinic in a year (count variable starting from 1; range 1-66, mean 4.2, SD 4.7, Var 22.5 Sk 4.6, Kur 37.8)

My co-variates are age (continuous from 0 to 100), gender (binary), and size of clinic (categorical; 4 categories)

The syntax I use is

Code:

nbreg noofvisitspy age i.gender_v i.clinicsize , ll(0)

Code:

margins gender_v, atmeans

The model output is as follows:

and the estimate output is as follows:

0.75 visits per patient in a year for males ( or 0.9 for females) doesn't make sense when the lowest number of visits is 1. Why am I getting less than 1? Is there a step that I am missing (changing distribution, etc.) , or am I doing something completely wrong?

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