
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21982.09     174.225    22903.13    21640.59    22323.59
experime |  17,281    21666.15    172.0157     22612.7    21328.98    22003.32
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            315.9433    244.8341               -163.9395    795.8262
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    diff = mean(control) - mean(experime)                         t =   1.2904
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9015         Pr(|T| > |t|) = 0.1969          Pr(T > t) = 0.0985
