Escarlett Gac
Chapter 8 Homework
Pat I
A random sample of 15 customers’ waiting time in a bank was selected, giving the following
results in minutes:
0.38 2.34 3.02 3.2 3.54 3.79 4.21 4.5 4.77 5.1 5.13 5.55 6.1 6.19 6.46
1) Based on the sample above, what is the point estimate of the true mean (same as the
Population mean) of customers’ waiting time in a bank?
The point estimate of the True population is = (0.38 + 2.34 + 3.02 +..... + 6.46)/15 = 4.28
2) Based on the sample above, what is the point estimate of the true population (same as the
population proportion) of customer who waited more than 4.5 minutes?
Point estimate= 0.467
3) To estimate the true mean of customers’ waiting time in a bank, how large a sample must be
taken to insure the estimate is off by no more than + 2% with 99% certainty if the population
standard deviation is known to be 2.68?
0.02. ≥ 2.576 x 2.68/√n =
N ≥ 119151.99
Simple size: 119152
4) What would happen to the sample size above if the error was increased to 4%?
As the error increases to 4% the sample size decreases.
Part II
A bottle of water distributor wants to estimate the amount of water contained in 1-gallon bottles
purchased from a nationally known water bottling company. The water bottling company’s
specifications state that the standard deviation of the amount of water is equal to 0.02 gallon. A
random sample of 50 bottle is selected, and the sample mean amount of water per 1-gallon bottle
is 0.995 gallon.
n= 50, =0.02, = 0.995, =1
a) Construct a 99% confidence interval estimate for the population mean amount of water
included in a 1-gallon bottle.
c = 99%
formula for confidence interval is
Chapter 8 Homework
Pat I
A random sample of 15 customers’ waiting time in a bank was selected, giving the following
results in minutes:
0.38 2.34 3.02 3.2 3.54 3.79 4.21 4.5 4.77 5.1 5.13 5.55 6.1 6.19 6.46
1) Based on the sample above, what is the point estimate of the true mean (same as the
Population mean) of customers’ waiting time in a bank?
The point estimate of the True population is = (0.38 + 2.34 + 3.02 +..... + 6.46)/15 = 4.28
2) Based on the sample above, what is the point estimate of the true population (same as the
population proportion) of customer who waited more than 4.5 minutes?
Point estimate= 0.467
3) To estimate the true mean of customers’ waiting time in a bank, how large a sample must be
taken to insure the estimate is off by no more than + 2% with 99% certainty if the population
standard deviation is known to be 2.68?
0.02. ≥ 2.576 x 2.68/√n =
N ≥ 119151.99
Simple size: 119152
4) What would happen to the sample size above if the error was increased to 4%?
As the error increases to 4% the sample size decreases.
Part II
A bottle of water distributor wants to estimate the amount of water contained in 1-gallon bottles
purchased from a nationally known water bottling company. The water bottling company’s
specifications state that the standard deviation of the amount of water is equal to 0.02 gallon. A
random sample of 50 bottle is selected, and the sample mean amount of water per 1-gallon bottle
is 0.995 gallon.
n= 50, =0.02, = 0.995, =1
a) Construct a 99% confidence interval estimate for the population mean amount of water
included in a 1-gallon bottle.
c = 99%
formula for confidence interval is
