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# st: Using a Tobit regression with the Heckman correction

 From "J. Boreham" To statalist@hsphsun2.harvard.edu Subject st: Using a Tobit regression with the Heckman correction Date 17 Dec 2011 21:16:18 +0000

```Dear Statalist,

```
I'm very new to Stata, so apologise if this is a silly question. I'm looking to run a Tobit regression using the Heckman correction. My Heckman code is:
```
```
***** heckman fee age agesq curr_app curr_goal_d curr_goal_m curr_goal_f, /// select(transferred = age agesq curr_app curr_goal_d curr_goal_m curr_goal_f prom) twostep *****
```
```
But this uses OLS rather than a Tobit model. I instead attempted to create the two stage Heckman correction by first manually producing the inverse Mills ratio, and then running a Tobit regression:
```
```
***** probit transferred age agesq curr_app curr_goal_d curr_goal_m curr_goal_f prom
```
predict predicted_values, xb

generate denominator = normal(predicted_values)
generate numerator = normalden(predicted_values)
generate mills_ratio = numerator/denominator

tobit fee age agesq curr_app curr_goal_d curr_goal_m curr_goal_f mills_ratio
*****

```
However, this will not account for the non-standard errors one needs when using the Heckman correction.
```
```
So is it possible either to tell Stata to use a Tobit regression with the "heckman" command, or instead to get the correct standard errors when manually doing the correction by inserting the inverse Mills ratio?
```

Thanks for your consideration,

John Boreham
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```