
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21981.56    174.3567    22920.44    21639.81    22323.32
experime |  17,281    21666.68    171.8822    22595.16    21329.77    22003.59
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |             314.885    244.8341               -164.9979    794.7679
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    diff = mean(control) - mean(experime)                         t =   1.2861
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9008         Pr(|T| > |t|) = 0.1984          Pr(T > t) = 0.0992
