
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21801.77    171.5811    22555.58    21465.46    22138.09
experime |  17,281    21846.47    174.6611    22960.46    21504.12    22188.82
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -44.69861    244.8399               -524.5928    435.1956
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    diff = mean(control) - mean(experime)                         t =  -0.1826
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.4276         Pr(|T| > |t|) = 0.8551          Pr(T > t) = 0.5724
