Test that there is no difference between the earnings of workers assigned to the treatment group and those assigned to the control group in 1975, before the start of the program. Show the STATA command and its output. Conclude using a 5% significance level.

ttest re75, by(treat)

Two-sample t test with equal variances

------------------------------------------------------------------------------

Group | Obs Mean Std. err. Std. dev. [95% conf. interval]

---------+--------------------------------------------------------------------

0 | 425 3026.683 252.2977 5201.25 2530.773 3522.593

1 | 297 3066.098 282.8697 4874.889 2509.407 3622.789

---------+--------------------------------------------------------------------

Combined | 722 3042.897 188.5423 5066.143 2672.739 3413.054

---------+--------------------------------------------------------------------

diff | -39.41544 383.4172 -792.1647 713.3338

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diff = mean(0) - mean(1) t = -0.1028

H0: diff = 0 Degrees of freedom = 720

Ha: diff < 0 Ha: diff != 0 Ha: diff > 0

Pr(T < t) = 0.4591 Pr(|T| > |t|) = 0.9182 Pr(T > t) = 0.5409

.

end of do-file