In: Statistics and Probability
A national air traffic control system handled an average of 47,651 flights during 28 randomly selected days in a recent year. The standard deviation for this sample is 6,496 flights per day. Complete parts a through c below.
a. Construct a 99% confidence interval to estimate the average number of flights per day handled by the system.
The 99% confidence interval to estimate the average number of flights per day handled by the system is from a lower limit of_______ to an upper limit of ___________ .
A national air traffic control system handled an average of 47,132 flights during 29 randomly selected days in a recent year. The standard deviation for this sample is 6,168 flights per day. Complete parts a through c below.
a. Construct a 99% confidence interval to estimate the average
number of flights per day handled by the system.
The 99% confidence interval to estimate the average number of
flights per day handled by the system is from a lower limit of
____________ to an upper limit of____________
Solution :
a ) Given that,
= 47,651
s = 6,496
n = 28
Degrees of freedom = df = n - 1 = 28 - 1 = 27
At 99% confidence level the t is ,
= 1 - 99% = 1 - 0.99 = 0.01
/ 2 = 0.01 / 2 = 0.005
t /2,df = t0.005,27 =2.771
Margin of error = E = t/2,df * (s /n)
= 2.771 * (6,496/ 28)
= 3401.76
Margin of error = 3401.76
The 99% confidence interval estimate of the population mean is,
- E < < + E
47,651 - 3401.76< < 47,651 +3401.76
44249.24 < < 51052.76
upper limit of =51052.76
lower limit of = 44249.24
b ) Given that,
= 47,132
s = 6,168
n = 29
Degrees of freedom = df = n - 1 = 29 - 1 = 28
At 99% confidence level the t is ,
= 1 - 99% = 1 - 0.99 = 0.01
/ 2 = 0.01 / 2 = 0.005
t /2,df = t0.005,28 =2.763
Margin of error = E = t/2,df * (s /n)
= 2.763 * ( 6,168 / 29)
= 3164.65
Margin of error = 3164.65
The 99% confidence interval estimate of the population mean is,
- E < < + E
47,132 - 3164.65 < < 47,132 + 3164.65
43967.34 < < 50296.65
upper limit of =50296.65
lower limit of = 43967.34