number 20

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

a. Express the confidence interval in the format that uses the"less than" symbol. Given that the original listed data use one decimalplace, round the confidence interval limits accordingly.

------- Mbps<< ------- Mbps

(Round to two decimal places asneeded.)

b. Identify the best point estimate of and the margin of error.

The point estimate of is ------- Mbps.

(Round to two decimal places asneeded.)

The margin of error is E= --------- (Round to two decimal places asneeded.)

c. In constructing the confidence interval estimate of , why is it not necessary to confirm that the sample data appear to be from a population with a normaldistribution?

1- Because the sample standard deviation isknown, the normal distribution can be used to construct the confidence interval.

2-

Because the sample size of 50 is greater than30, the distribution of sample means can be treated as a normal distribution.

3- Because the population standard deviation isknown, the normal distribution can be used to construct the confidence interval.

4-

Because the sample is a randomsample, the distribution of sample means can be treated as a normal distribution.