QUESTION 4 - ANSWER

Income also affects households' total monthly food expenditure. Try a simple regression of mxtfood on total monthly income. Write an equation for this relationship and interpret the result.

There are a few variables that would explain monthly income of households. Use the lookfor command to find the appropriate one.

lookfor income

267. farmrent int %9.0g crop rental income
268. liverent int %9.0g grazing rental income
269. rentinc float %9.0g rental income
281. agincome float %9.0g value of ag. income
283. otherinc float %9.0g household other income
285. totminc float %9.0g total monthy income

Now, try the regression as follows:

sort hhid
reg mxtfood totminc if hhid~=hhid[_n-1]

  Source |       SS       df       MS                  Number of obs =    1026
---------+------------------------------               F(  1,  1024) =   65.37
   Model |  10156513.2     1  10156513.2               Prob > F      =  0.0000
Residual |   159108791  1024  155379.679               R-squared     =  0.0600
---------+------------------------------               Adj R-squared =  0.0591
   Total |   169265304  1025  165136.882               Root MSE      =  394.18

------------------------------------------------------------------------------
 mxtfood |      Coef.   Std. Err.       t     P>|t|       [95% Conf. Interval]
---------+--------------------------------------------------------------------
 totminc |    .021563   .0026671      8.085   0.000       .0163295    .0267966
   _cons |   493.7278   13.30798     37.100   0.000       467.6138    519.8419
------------------------------------------------------------------------------

The equation made by these coefficients equals:

(predicted mxtfood)i= 493.7278 + .0211563(totminc)i

For every 1000 rand increase in total monthly household income, monthly household food expenditure increases by approximately 20 rand. From the regression table, t-values for constant and totminc both exceed 2, which implies these coefficients are significant. Also, R-squared value implies that variance of monthly food expenditure explained by total monthly income is 6%. Keep in mind, though, that we have not checked for outliers.

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