Among the indicators of patient condition after pyloromyotomy (correction of stenotic pylorus) in neonates is time (hours) to full feeding. 21 A surgeon wants to place a 95 % confidence interval on mean time to full feeding. He has readings from n = 20 infants. Some of the data are 3.50, 4.52, 3.03, 14.53, .... He calculates m = 6.56 hours and s = 4.57 hours.

What is the 95% confidence interval?