
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21867.89     173.071    22751.43    21528.65    22207.12
experime |  17,281    21780.36    173.1844    22766.34     21440.9    22119.81
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            87.53022    244.8396               -392.3633    567.4237
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    diff = mean(control) - mean(experime)                         t =   0.3575
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.6396         Pr(|T| > |t|) = 0.7207          Pr(T > t) = 0.3604
