
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21636.76    172.1891     22635.5    21299.25    21974.27
experime |  17,281    22011.48    174.0502    22880.16    21670.33    22352.64
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -374.7249    244.8317                -854.603    105.1532
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    diff = mean(control) - mean(experime)                         t =  -1.5305
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.0629         Pr(|T| > |t|) = 0.1259          Pr(T > t) = 0.9371
