
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21741.33    172.1244    22626.99    21403.95    22078.72
experime |  17,281    21906.91    174.1236     22889.8    21565.61    22248.21
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -165.5739    244.8384               -645.4652    314.3173
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    diff = mean(control) - mean(experime)                         t =  -0.6763
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.2494         Pr(|T| > |t|) = 0.4989          Pr(T > t) = 0.7506
