Results Among 371 randomized patients (mean [SD] age,  years; 136 [%] women), 371 completed the trial. The proportion of patients with successful first-pass intubation did not differ significantly between the video laryngoscopy and direct laryngoscopy groups (% vs %; absolute difference, −% [95% CI, −% to %]; P = .60). The proportion of first-attempt intubations performed by nonexperts (primarily residents, n = 290) did not differ between the groups (% with video laryngoscopy vs % with direct laryngoscopy; absolute difference % [95% CI, −% to %]; P = .76). The median time to successful intubation was 3 minutes (range, 2 to 4 minutes) for both video laryngoscopy and direct laryngoscopy (absolute difference, 0 [95% CI, 0 to 0]; P = .95). Video laryngoscopy was not associated with life-threatening complications (24/180 [%] vs 17/179 [%] for direct laryngoscopy; absolute difference, % [95% CI, −% to %]; P = .25). In post hoc analysis, video laryngoscopy was associated with severe life-threatening complications (17/179 [%] vs 5/179 [%] for direct laryngoscopy; absolute difference, % [95% CI, % to %]; P = .01) but not with mild to moderate life-threatening complications (10/181 [%] vs 14/181 [%]; absolute difference, −% [95% CI, −% to %]; P = .37).
The number of treatment units (subjects or groups of subjects) assigned to control and treatment groups, affects an RCT's reliability. If the effect of the treatment is small, the number of treatment units in either group may be insufficient for rejecting the null hypothesis in the respective statistical test . The failure to reject the null hypothesis would imply that the treatment shows no statistically significant effect on the treated in a given test . But as the sample size increases, the same RCT may be able to demonstrate a significant effect of the treatment, even if this effect is small.