
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21929.27    174.5465     22945.4    21587.14    22271.39
experime |  17,281    21718.98    171.6941    22570.43    21382.44    22055.51
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            210.2889    244.8374               -269.6003    690.1782
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    diff = mean(control) - mean(experime)                         t =   0.8589
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8048         Pr(|T| > |t|) = 0.3904          Pr(T > t) = 0.1 952
