
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21784.39    173.1777    22765.45    21444.94    22123.84
experime |  17,281    21863.85    173.0779    22752.33     21524.6     22203.1
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -79.46305    244.8396               -559.3567    400.4306
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    diff = mean(control) - mean(experime)                         t =  -0.3246
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.3728         Pr(|T| > |t|) = 0.7455          Pr(T > t) = 0.6272
