
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21952.54    174.7582    22973.23    21609.99    22295.08
experime |  17,281    21695.71    171.4767    22541.86    21359.59    22031.82
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            256.8288    244.8361               -223.0579    736.7156
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    diff = mean(control) - mean(experime)                         t =   1.0490
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8529         Pr(|T| > |t|) = 0.2942          Pr(T > t) = 0.1471
