
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281     21969.6    174.6401     22957.7    21627.28    22311.91
experime |  17,281    21678.65    171.5955    22557.47     21342.3    22014.99
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            290.9502     244.835               -188.9344    770.8348
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    diff = mean(control) - mean(experime)                         t =   1.1884
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8826         Pr(|T| > |t|) = 0.2347          Pr(T > t) = 0.1174
