
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21771.45     171.827     22587.9    21434.65    22108.25
experime |  17,281    21876.79    174.4184    22928.56    21534.92    22218.67
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -105.3458    244.8393               -585.2389    374.5473
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    diff = mean(control) - mean(experime)                         t =  -0.4303
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.3335         Pr(|T| > |t|) = 0.6670          Pr(T > t) = 0.6665
