
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21858.75    173.3349    22786.13       21519    22198.51
experime |  17,281    21789.49    172.9205    22731.64    21450.55    22128.43
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            69.26136    244.8397               -410.6325    549.1552
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    diff = mean(control) - mean(experime)                         t =   0.2829
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6114         Pr(|T| > |t|) = 0.7773          Pr(T > t) = 0.3886
