
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281     21835.2    174.0654    22882.15    21494.01    22176.38
experime |  17,281    21813.05    172.1855    22635.03    21475.54    22150.55
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            22.15117      244.84               -457.7432    502.0455
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    diff = mean(control) - mean(experime)                         t =   0.0905
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.5360         Pr(|T| > |t|) = 0.9279          Pr(T > t) = 0.4640
