* Linear OLS Models for Weekly Wages in India
*
* Keywords:
*     regression, ols, linear, dummy, interaction, ancova, wages, india
*
* Description:
*     We illustrate how to estimate OLS Models with Quantitative and 
*     Interaction variables for Weekly Wages in a town in Southern India
*
* Author(s):
*     Skif Pankov
*
* Source:
*    Damodar N. Gujarati and Dawn C. Porter, Basic Econometrics - 5th Edition
*    McGraw-Hill International Edition, Chapter 9, Example 9.12 (page 300)
*
sample 1 114

* Reading the datafile and naming variables
read(data_9.12.shd) wi age de2 de3 de4 dpt dsex

* Generating a natural logarithm of wi under a name lnwi
genr lnwi = log(wi)

* Generating interraction dummies
genr dsxde2 = dsex*de2
genr dsxde3 = dsex*de3
genr dsxde4 = dsex*de4

* Running an OLS regression of lnwi on age and original dummy variables,
* stating to include residual statistics and that it is a log-linear regression 
ols lnwi age de2 de3 de4 dpt dsex / rstat loglin

* Running two other OLS regression of lnwi on age and available dummy 
* variables, stating to include residual statistics and that it is a log-linear 
* regression 
ols lnwi age de2 de3 de4 dsxde2 dsxde3 dsxde4 dpt dsex / rstat loglin

ols lnwi age dsxde2 dsxde3 dsxde4 dpt dsex / rstat loglin

stop

* Note: 
*     the dataset for this regression available from the publisher did not
*     include all the 261 observations used by the author, hence the results
*     will not exactly match those in the book, but will be close