
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21838.37    174.8363     22983.5    21495.67    22181.07
experime |  17,281    21809.87    171.4026    22532.11     21473.9    22145.84
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            28.50086      244.84               -451.3934    508.3952
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    diff = mean(control) - mean(experime)                         t =   0.1164
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.5463         Pr(|T| > |t|) = 0.9073          Pr(T > t) = 0.4537
