
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21899.84    172.4485     22669.6    21561.82    22237.85
experime |  17,281     21748.4     173.803    22847.65    21407.73    22089.08
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            151.4322    244.8386               -328.4596    631.3239
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    diff = mean(control) - mean(experime)                         t =   0.6185
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7319         Pr(|T| > |t|) = 0.5363          Pr(T > t) = 0.2681
