
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21787.31    171.6051    22558.73    21450.95    22123.67
experime |  17,281    21860.93    174.6372    22957.32    21518.62    22203.24
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -73.62043    244.8397               -553.5142    406.2733
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    diff = mean(control) - mean(experime)                         t =  -0.3007
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.3818         Pr(|T| > |t|) = 0.7637          Pr(T > t) = 0.6182
