
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21946.82     175.313    23046.16    21603.19    22290.46
experime |  17,281    21701.42      170.91    22467.36    21366.42    22036.42
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            245.4063    244.8364               -234.4812    725.2937
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    diff = mean(control) - mean(experime)                         t =   1.0023
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8419         Pr(|T| > |t|) = 0.3162          Pr(T > t) = 0.1581
