
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21689.21    170.8691    22461.98    21354.29    22024.13
experime |  17,281    21959.03    175.3518    23051.27    21615.33    22302.74
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            -269.824    244.8357               -749.7099     210.062
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    diff = mean(control) - mean(experime)                         t =  -1.1021
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1352         Pr(|T| > |t|) = 0.2704          Pr(T > t) = 0.8648
