
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21985.52    175.1576    23025.73     21642.2    22328.85
experime |  17,281    21662.72    171.0656     22487.8    21327.41    21998.02
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            322.8062    244.8338               -157.0761    802.6886
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    diff = mean(control) - mean(experime)                         t =   1.3185
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.9063         Pr(|T| > |t|) = 0.1874          Pr(T > t) = 0.0937
