
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21847.18    171.6607    22566.04    21510.71    22183.65
experime |  17,281    21801.06    174.5829    22950.18    21458.86    22143.26
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            46.12112    244.8399                -433.773    526.0153
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    diff = mean(control) - mean(experime)                         t =   0.1884
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.5747         Pr(|T| > |t|) = 0.8506          Pr(T > t) = 0.4253
