
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21694.49    171.3435    22524.34    21358.64    22030.34
experime |  17,281    21953.76    174.8888    22990.39    21610.96    22296.55
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -259.2681     244.836               -739.1547    220.6185
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    diff = mean(control) - mean(experime)                         t =  -1.0589
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1448         Pr(|T| > |t|) = 0.2896          Pr(T > t) = 0.8552
