
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21965.53    174.5029    22939.66    21623.49    22307.58
experime |  17,281    21682.71    171.7354    22575.86    21346.09    22019.33
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            282.8217    244.8353               -197.0635    762.7068
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    diff = mean(control) - mean(experime)                         t =   1.1552
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8760         Pr(|T| > |t|) = 0.2480          Pr(T > t) = 0.1240
