
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21838.27    171.6384    22563.11    21501.84     22174.7
experime |  17,281    21809.97    174.6048    22953.07    21467.73    22152.21
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            28.30193      244.84               -451.5924    508.1962
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    diff = mean(control) - mean(experime)                         t =   0.1156
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.5460         Pr(|T| > |t|) = 0.9080          Pr(T > t) = 0.4540
