
Two-sample t test with equal variances
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   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21679.33    171.0585    22486.87    21344.04    22014.62
experime |  17,281    21968.91    175.1662    23026.86    21625.57    22312.26
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -289.5852     244.835               -769.4698    190.2995
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    diff = mean(control) - mean(experime)                         t =  -1.1828
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1185         Pr(|T| > |t|) = 0.2369          Pr(T > t) = 0.8815
