------------------------------------------------------------------------------------------------------------- . describe Observations: 209 Wooldridge, Introductory Econometrics Variables: 4 3 Feb 2025 18:06 (_dta has notes) ------------------------------------------------------------------------------------------------------------- Variable Storage Display Value name type format label Variable label ------------------------------------------------------------------------------------------------------------- salary long %13.0g 1990 salary, thousands $ sales double %9.0g 1990 firm sales, millions $ roe double %9.0g return on equity, 1988-90 average finance byte %13.0g activity =1 if financial firm ------------------------------------------------------------------------------------------------------------- Sorted by: finance . summarize salary sales roe, detail 1990 salary, thousands $ ------------------------------------------------------------- Percentiles Smallest 1% 333 223 5% 448 256 10% 525 333 Obs 209 25% 736 360 Sum of wgt. 209 50% 1039 Mean 1281.12 Largest Std. dev. 1372.345 75% 1407 4143 90% 1900 6640 Variance 1883332 95% 2327 11233 Skewness 6.854923 99% 6640 14822 Kurtosis 60.54128 1990 firm sales, millions $ ------------------------------------------------------------- Percentiles Smallest 1% 298.7 175.2 5% 764.7 181.5 10% 1212.3 298.7 Obs 209 25% 2210.3 514.1 Sum of wgt. 209 50% 3705.2 Mean 6923.793 Largest Std. dev. 10633.27 75% 7177 44323 90% 14932.1 57662 Variance 1.13e+08 95% 20659 69018 Skewness 4.999125 99% 57662 97649.9 Kurtosis 35.29968 return on equity, 1988-90 average ------------------------------------------------------------- Percentiles Smallest 1% 2.1 .5 5% 6.8 1.9 10% 8.9 2.1 Obs 209 25% 12.4 2.9 Sum of wgt. 209 50% 15.5 Mean 17.18421 Largest Std. dev. 8.518509 75% 20 44.4 90% 26.8 44.5 Variance 72.56499 95% 35.1 48.1 Skewness 1.56082 99% 44.5 56.3 Kurtosis 6.678555 . tabstat salary sales roe, statistics( mean max min range cv ) by(finance) Summary statistics: Mean, Max, Min, Range, CV Group variable: finance (=1 if financial firm) finance | salary sales roe --------------+------------------------------ non-financial | 1263.117 7228.507 17.99018 | 14822 97649.9 56.3 | 223 175.2 1.9 | 14599 97474.7 54.4 | 1.15741 1.6208 .4991844 --------------+------------------------------ financial | 1344.913 5844.048 14.32826 | 6640 24332 33.3 | 441 834.4 .5 | 6199 23497.6 32.8 | .7456342 .8881532 .4092718 --------------+------------------------------ Total | 1281.12 6923.793 17.18421 | 14822 97649.9 56.3 | 223 175.2 .5 | 14599 97474.7 55.8 | 1.071208 1.535758 .4957172 --------------------------------------------- . * See oli kirjeldav statistika . tabulate finance =1 if | financial | firm | Freq. Percent Cum. --------------+----------------------------------- non-financial | 163 77.99 77.99 financial | 46 22.01 100.00 --------------+----------------------------------- Total | 209 100.00 . * Korrelatsioonimaatriks kahes grupis eraldi . by finance, sort : pwcorr salary sales roe, star(5) ------------------------------------------------------------------------------------------------------------- -> finance = non-financial | salary sales roe -------------+--------------------------- salary | 1.0000 sales | 0.1158 1.0000 roe | 0.1574* -0.0530 1.0000 ------------------------------------------------------------------------------------------------------------- -> finance = financial | salary sales roe -------------+--------------------------- salary | 1.0000 sales | 0.1993 1.0000 roe | -0.1695 -0.2357 1.0000 . twoway (scatter salary sales) . generate l_salary = ln(salary) . generate l_sales = ln(sales) . regress l_salary l_sales roe finance Source | SS df MS Number of obs = 209 -------------+---------------------------------- F(3, 205) = 29.20 Model | 19.9733237 3 6.65777457 Prob > F = 0.0000 Residual | 46.7488395 205 .22804312 R-squared = 0.2994 -------------+---------------------------------- Adj R-squared = 0.2891 Total | 66.7221632 208 .320779631 Root MSE = .47754 ------------------------------------------------------------------------------ l_salary | Coefficient Std. err. t P>|t| [95% conf. interval] -------------+---------------------------------------------------------------- l_sales | .2737841 .0329345 8.31 0.000 .2088503 .338718 roe | .0194431 .003978 4.89 0.000 .0116 .0272862 finance | .1826565 .0810419 2.25 0.025 .022874 .3424391 _cons | 4.305779 .2920834 14.74 0.000 3.729907 4.881652 ------------------------------------------------------------------------------ . estat imtest, white White's test H0: Homoskedasticity Ha: Unrestricted heteroskedasticity chi2(8) = 1.43 Prob > chi2 = 0.9938 Cameron & Trivedi's decomposition of IM-test -------------------------------------------------- Source | chi2 df p ---------------------+---------------------------- Heteroskedasticity | 1.43 8 0.9938 Skewness | 3.18 3 0.3642 Kurtosis | 2.20 1 0.1378 ---------------------+---------------------------- Total | 6.82 12 0.8693 -------------------------------------------------- . estat ovtest Ramsey RESET test for omitted variables Omitted: Powers of fitted values of l_salary H0: Model has no omitted variables F(3, 202) = 2.30 Prob > F = 0.0787 -------------------------------------------------------------------------------------------------------------