
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21892.33    171.2577    22513.06    21556.65    22228.01
experime |  17,281    21755.91    174.9768    23001.97    21412.94    22098.89
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            136.4163    244.8389               -343.4759    616.3085
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    diff = mean(control) - mean(experime)                         t =   0.5572
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7113         Pr(|T| > |t|) = 0.5774          Pr(T > t) = 0.2887
