Refer to the accompanying data display that results from a sample of airport data speeds in mbps. complete parts (a) through (c) below.

tinterval
(13.046,22.15)
x=17.598
sx=16.01712719
n=50

i. express the confidence interval in the format that uses the "less than" symbol. given that the original listed data use one decimal place, round the confidence interval limits accordingly. round to
two decimal places as needed.
ii. identify the best point estimate of μ and the margin of error.
iii. in constructing the confidence interval estimate of μ, why is it not necessary to confirm that the sample data appear to be from a population with a normaldistribution?

a. because the sample standard deviation is known, the normal distribution can be used to construct the confidence interval.
b. because the sample is a random sample, it can be assumed that the sample mean is from a population with a normal distribution.
c. because the population standard deviation is known, the normal distribution can be used to construct the confidence interval.
d. because the sample size of 50 is greater than 30, it can be assumed that the sample mean is from a population with a normal distribution.