
Two-sample t test with equal variances
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   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21681.41    172.5166    22678.55    21343.26    22019.56
experime |  17,281    21966.83    173.7305    22838.13    21626.31    22307.36
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -285.4279    244.8352               -765.3128    194.4571
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    diff = mean(control) - mean(experime)                         t =  -1.1658
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.1219         Pr(|T| > |t|) = 0.2437          Pr(T > t) = 0.8781
