
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281    21808.99    174.5286    22943.05     21466.9    22151.08
experime |  17,281    21839.25    171.7159     22573.3    21502.67    22175.83
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |           -30.26323      244.84               -510.1575    449.6311
------------------------------------------------------------------------------
    diff = mean(control) - mean(experime)                         t =  -0.1236
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.4508         Pr(|T| > |t|) = 0.9016          Pr(T > t) = 0.5 492
