ttest pc_nc, by (reopen) reverse Two-sample t test with equal variances Group Obs Mean Std. err. Std. dev. [95% conf. interval] Early 31 367 . 042 35 . 2502 196.2648 295. 0515 439.0325 Delayed 20 271 . 8011 31 . 09075 139 . 0421 206.7275 336. 8748 Combined 51 329. 6927 25. 30744 180.7313 278 . 8612 380.5242 diff 95 . 24088 50.56259 -6.368456 196. 8502 diff = mean (Early ) - mean (Delayed) t = 1. 8836 10: diff = 0 Degrees of freedom = 49 Ha: diff 0 Pr (T |t|) = 0. 0656 Pr(T > t) = 0.0328