
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21646.95    172.8843    22726.89    21308.08    21985.82
experime |  17,281    22001.29    173.3609    22789.55    21661.48     22341.1
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -354.3381    244.8326               -834.2179    125.5418
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    diff = mean(control) - mean(experime)                         t =  -1.4473
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0739         Pr(|T| > |t|) = 0.1478          Pr(T > t) = 0.9261
