
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21818.07    174.3346    22917.54    21476.36    22159.79
experime |  17,281    21830.17     171.913    22599.21     21493.2    22167.14
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -12.09685      244.84               -491.9912    467.7975
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    diff = mean(control) - mean(experime)                         t =  -0.0494
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.4803         Pr(|T| > |t|) = 0.9606          Pr(T > t) = 0.5197
