A study conducted by an airline showed that a random sample of nine of its passengers disembarking at the Cleveland airport, took an average of 24.1 minutes to claim their luggage. From a previous survey it was willing to assume that time to claim luggage is normally distributed with a variance of 18 (min)2. A 95% confidence interval for the mean time to claim one's luggage has endpoints.
Answer

24.1 ± 8.32

24.1 ± 3.92

24.1 ± 2.77

24.1 ± 3.26

24.1 ± 9.78

Question

A study conducted by an airline showed that a random sample of nine of its passengers disembarking at the Cleveland airport, took an average of 24.1 minutes to claim their luggage. From a previous survey it was willing to assume that time to claim luggage is normally distributed with a variance of 18 (min)2. A 95% confidence interval for the mean time to claim one's luggage has endpoints.
Answer
		
24.1 ± 8.32
		
24.1 ± 3.92
		
24.1 ± 2.77
		
24.1 ± 3.26
		
24.1 ± 9.78

anonymous · Answer

95% CI for the MEAN is = mean +- 2 SE  approx

SE = standard error of the mean 
SE = std dev/sqrt(number in sample)

SE = sqrt(18)/sqrt(9) = sqrt(2)

95%CI = mean + 2sqrt(2)  approx.

 = 24.1 + 2.77 from options given