
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21796.29    172.6985    22702.47    21457.79     22134.8
experime |  17,281    21851.95    173.5562    22815.21    21511.76    22192.14
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -55.65823    244.8398               -535.5523    424.2358
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    diff = mean(control) - mean(experime)                         t =  -0.2273
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.4101         Pr(|T| > |t|) = 0.8202          Pr(T > t) = 0.5 899
