OLS Observation Count

[Vlad Nesterovich]

Hi,

I am running an OLS regression in which the main regressor variable is a binary variable. I would like to know in the case I have for instance 9,300 observations, how many of those are 1s and 0s. Many thanks!

Kind regards,
Vlad

[Nick Cox]

. sysuse auto, clear
(1978 Automobile Data)

. regress mpg foreign

      Source |       SS           df       MS      Number of obs   =        74
-------------+----------------------------------   F(1, 72)        =     13.18
       Model |  378.153515         1  378.153515   Prob > F        =    0.0005
    Residual |  2065.30594        72  28.6848048   R-squared       =    0.1548
-------------+----------------------------------   Adj R-squared   =    0.1430
       Total |  2443.45946        73  33.4720474   Root MSE        =    5.3558

------------------------------------------------------------------------------
         mpg |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
     foreign |   4.945804   1.362162     3.63   0.001     2.230384    7.661225
       _cons |   19.82692   .7427186    26.70   0.000     18.34634    21.30751
------------------------------------------------------------------------------

. tab foreign if e(sample)

   Car type |      Freq.     Percent        Cum.
------------+-----------------------------------
   Domestic |         52       70.27       70.27
    Foreign |         22       29.73      100.00
------------+-----------------------------------
      Total |         74      100.00

. tab foreign if e(sample), nola

   Car type |      Freq.     Percent        Cum.
------------+-----------------------------------
          0 |         52       70.27       70.27
          1 |         22       29.73      100.00
------------+-----------------------------------
      Total |         74      100.00

The qualifier

if e(sample)

spells out "for observations included in the previous regression", which is often important.

[Vlad Nesterovich]

Thank you Nick! This answered my question.

Kind regards,
Vlad