
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281     21787.2    172.1359    22628.51     21449.8     22124.6
experime |  17,281    21861.04    174.1141    22888.55    21519.76    22202.32
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -73.84418    244.8397               -553.7379    406.0496
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    diff = mean(control) - mean(experime)                         t =  -0.3016
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.3815         Pr(|T| > |t|) = 0.7630          Pr(T > t) = 0.6185
