
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    22074.69    174.9285    22995.61    21731.82    22417.57
experime |  17,281    21573.55    171.2874    22516.97    21237.81    21909.29
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            501.1451    244.8252                21.27975    981.0104
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    diff = mean(control) - mean(experime)                         t =   2.0470
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9797         Pr(|T| > |t|) = 0.0407          Pr(T > t) = 0.0203
