Hello everyone,

First post here and I have to say I really enjoy my first months with Stata, even though I'm learning it pretty much under pressure of a timeline and a project.

I have a large dataset, total number of obs/participants:127535. Dependent variable: death vs injury (dichotomous). I have to deal with a missing data issue. Two of my independent variables under investigation have a large percentage of missing data. Use of helmet for bike riders and use of seatbelt for 4-wheel vehicle drivers, around 33% and 46% respectively. How am I going to continue?

The data seems not to be MCAR. The variable “geocode” shows that for one specific city, unknown may reach 80%, while for another may be below 10%. This is mostly due to a different approach from police departments around the country on the standard RTA form.

What’s more is that missingness seems naturally to be related with the dependent variable under investigation “outcome” (death vs inj/no inj). For example, we have the following results on whether a bike rider wore a helmet at the time of an accident. Yes:44% No:22% Unknown(missing):34%. However, if we stratify by severity, for the bike riders that had no or light injury, this information was missing at 36% and if severe injury or death was involved it was missing at 22%.

Is multiple imputation have a good idea and how am i going to proceed with the commands?

Thank you for your time,

Evangelos