2. Given that the investigators are interested in comparing the mean hours to recovery after surgery for two different procedures. Participants are randomized to receive one of the two treatments and then followed to full recovery. To determine: how does the precision of the study is affected when 25% of participants had dropped out of study. The precision of the study decreases when equal or unequal number of dropouts occur in groups. This will bias the results of statistics that are computed based on these available data. And, when the participants do not completely be missing at random among dropout this will bias or skew the results that are to be compared. Rarely, the drop out goes missing completely at random. Hence dropout will skew the results. 1. Interpretation for a 95% confidence interval by Normal approximation to the binomial calculation. Given: N = 1229 X= 614 Standard Error of the mean, SEM SEM = X (N-x) 0.0143 N3 (1 - Confidence Level) (1 - 0.95) a = 0.025 2 2 Standard Normal Deviation for a = Z, = 1.9600 Proportion of positive results, P = _ 614 0.499593 N 12299 Lower bound = P - (Za * SEM) = 0.4716 Upper bound = P + (Za * SEM) = 0.5275 @95% Confidence Interval (0.4716,0.5275) (0.4716