
Two-sample t test with equal variances
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   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21611.63    169.8935    22333.73    21278.63    21944.64
experime |  17,281    22036.61    176.2884    23174.38    21691.06    22382.15
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -424.9725    244.8293                -904.846    54.90097
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    diff = mean(control) - mean(experime)                         t =  -1.7358
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0413         Pr(|T| > |t|) = 0.0826          Pr(T > t) = 0.9587
