
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21855.32    171.7984    22584.14    21518.58    22192.07
experime |  17,281    21792.92    174.4472    22932.34    21450.98    22134.85
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            62.40694    244.8398                -417.487    542.3009
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    diff = mean(control) - mean(experime)                         t =   0.2549
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6006         Pr(|T| > |t|) = 0.7988          Pr(T > t) = 0.3994
