
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21974.81    175.0249    23008.29    21631.74    22317.88
experime |  17,281    21673.43    171.2024    22505.79    21337.86    22009.01
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            301.3781    244.8346               -178.5058     781.262
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    diff = mean(control) - mean(experime)                         t =   1.2309
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8908         Pr(|T| > |t|) = 0.2184          Pr(T > t) = 0.1092
