
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21845.19    173.0243     22745.3    21506.04    22184.34
experime |  17,281    21803.05    173.2315    22772.53     21463.5     22142.6
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |             42.1382    244.8399                -437.756    522.0324
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    diff = mean(control) - mean(experime)                         t =   0.1721
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.5683         Pr(|T| > |t|) = 0.8634          Pr(T > t) = 0.4317
