
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21966.16    173.8767    22857.35    21625.34    22306.97
experime |  17,281    21682.09    172.3693    22659.19    21344.22    22019.95
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            284.0702    244.8352               -195.8149    763.9552
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    diff = mean(control) - mean(experime)                         t =   1.1603
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8770         Pr(|T| > |t|) = 0.2460          Pr(T > t) = 0.1230
