A simple random sample of 60 items is taken from an inventory and the average unit cost on the items is $23.5. The population standard deviation σ is unknown. Instead the sample standard deviation s is also calculated from the sample and is found to be $12.2. (4 points)a)Construct a 99% confidence interval for the mean unit cost of the population.b)What is the margin of error at the 95% confidence level?
6.The average score on an employee satisfaction survey is found to be 3.75 (out of 5). The sample standard deviation is 1.24. These two statistics are calculated from a random sample of25 employees in a mid-size professional firm. (4 points)a)With 95% confidence, what is the margin of error?b)What is the 95% confidence interval estimate of the population mean score?7.Annual starting salary for graduates of the BBA program in a Canadian University is expected to be between $35,000 and $55,000. A survey involving a random sample of graduates from this program is planned and the first order of business is to decide on an appropriate sample size. As usual, the 95% level of confidence will be used. (6 points)a)What is the planning value for the population standard deviation to be used in the sample size formula for estimating the population-mean starting salary?b)How large should the sample size be if the desired margin of error is $1000?