PART A) You own a small storefront retail business and are interested in determining the average amount of money a typical customer spends per visit to your store. You take a random sample over the course of a month for 14 customers and find that the average dollar amount spent per transaction per customer is $109.477 with a standard deviation of $11.8571. Create a 90% confidence interval for the true average spent for all customers per transaction.
PART B) Researchers at a metals lab are testing a new alloy for use in high end electronics. The alloy is very expensive to make so their budget for testing is limited. The researchers need to estimate the average force required to bend a piece of the alloy to a 90 degree angle. From previous tests, the standard deviation is known to be 48.535 Newtons. In order to estimate the true mean within a margin of error of 12.979 Newtons with 95% confidence, how many samples would need to be tested?
PART C)
The owner of a local golf course wanted to determine the average age of the golfers that played on the course. In a random sample of 22 golfers that visited his course, the sample mean was 48.26 and the standard deviation was 5.207. Using this information, the owner calculated the confidence interval of (46.35, 50.17) with a confidence level of 90% for the average age. Which of the following is an appropriate interpretation of this confidence interval?









Solutionb:
From previous tests, the standard deviation is known to be 48.535 Newtons. In order to estimate the true mean within a margin of error of 12.979 Newtons with 95% confidence, how many samples would need to be tested?
MOE=E=12.979
z crit dor 95%=1.96
sd=48.535
n=z^2*sigma^2/E^2
=1.96^2*48.535^2/12.979^2
=53.72
n=54
required sample size=n=54
we need to sample 54
Solution2:
confidence interval allples for whole populationall
we are 90% confident that the true population mean of all lies in between 46.35 and 50.17
We are 90% confident that the average age of all golfers that play on the golf course is between 46.35 and 50.17. 
Get Answers For Free
Most questions answered within 1 hours.