
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281     21898.6    174.7568    22973.04    21556.06    22241.14
experime |  17,281    21749.65    171.4819    22542.53    21413.52    22085.77
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            148.9518    244.8387                 -330.94    628.8437
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    diff = mean(control) - mean(experime)                         t =   0.6084
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.7285         Pr(|T| > |t|) = 0.5429          Pr(T > t) = 0.2715
