Question

Noise levels at 5 airports were measured in decibels yielding the following data:

117,118,140,116,119
1. Construct the 90% confidence interval for the mean noise level at such locations. Assume the population is approximately normal.
2. Calculate the sample mean for the given sample data.
3. Find the critical value that should be used in constructing the confidence interval.

Answer 1

1. 112.364<μ,131.636

2. mean = 122

3. critical value = +-2.1318

Explanation:

117+118+140+116+119/5

= 610/5

= 122

the sample mean = 122

the sample standard deviation

s² = (117-122)²+(118-122)²+(140-122)²+(116-122²)+(119-122)²/5-1

= 25+16+324+36+9/4

= 410/4

= 102.5

s² = 102.5

s = √102.5

s= 10.12

SE = s/√n

= 10.12/√5

= 4.52

degree of freedom = 5-1 = 4

critical value of t = +-2.1318 using soft ware

confidence interval =

mean +- t(SE)

122-(2.1318)(4.52), 122+(2.1318)(4.52)

= [112.364, 131.636]

112.364<μ,131.636

therefore these are the answers in the ordre it was given in the question

1. 112.364<μ,131.636

2. mean = 122

3. critical value = +-2.1318