
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281     21920.1    174.5708    22948.59    21577.93    22262.28
experime |  17,281    21728.14    171.6701    22567.27    21391.65    22064.63
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            191.9666    244.8378               -287.9236    671.8567
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    diff = mean(control) - mean(experime)                         t =   0.7841
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7835         Pr(|T| > |t|) = 0.4330          Pr(T > t) = 0.2165
