
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21929.65    173.8119    22848.83    21588.96    22270.34
experime |  17,281    21718.59    172.4377    22668.18    21380.59    22056.58
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            211.0629    244.8374               -268.8263    690.9522
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    diff = mean(control) - mean(experime)                         t =   0.8621
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8057         Pr(|T| > |t|) = 0.3887          Pr(T > t) = 0.1943
