
Two-sample t test with equal variances
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   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21978.08    174.3693     22922.1     21636.3    22319.86
experime |  17,281    21670.16    171.8698    22593.53    21333.28    22007.04
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            307.9172    244.8344               -171.9662    787.8006
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    diff = mean(control) - mean(experime)                         t =   1.2577
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.8957         Pr(|T| > |t|) = 0.2085          Pr(T > t) = 0.1043
