
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281     21955.9    176.1086    23150.75    21610.71    22301.09
experime |  17,281    21692.34    170.0893    22359.47    21358.95    22025.73
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            263.5568    244.8359               -216.3295    743.4432
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    diff = mean(control) - mean(experime)                         t =   1.0765
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8591         Pr(|T| > |t|) = 0.2817          Pr(T > t) = 0.1409
