
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21849.01    173.1237    22758.36    21509.67    22188.35
experime |  17,281    21799.23    173.1322    22759.47    21459.87    22138.59
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            49.78125    244.8399               -430.1129    529.6754
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    diff = mean(control) - mean(experime)                         t =   0.2033
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.5806         Pr(|T| > |t|) = 0.8389          Pr(T > t) = 0.4194
