Question

1A survey of 25 grocery stores revealed that the average price of a gallon of milk was $2.98 with a standard error of $0.10.

a. A sample of 25 is selected from a known population of 100 elements.What is the finite population correction factor?

b. If 90% and 95% confidence intervals are developed to estimate the true cost of a gallon of milk, what similarities would they have?

c. What is the 98% confidence interval to estimate the true cost of a gallon of milk?

2 A pharmaceutical company wanted to estimate the population mean of monthly sales for their 250 sales people.Forty sales people were randomly selected.Their mean monthly sales were $10000 with a standard deviation of $1000.construct a 95% confidence interval for the population mean.

3.A bank wishes to estimate the mean balances owed by customers holding MasterCard.Te population standard deviation is estimated to br $300.Ifa 98 percent confidence interval is used and an interval of $75 is desired, how many cardholders should be sampled?

Answer 1

A survey of 25 grocery stores revealed that the average price of a gallon of milk was $2.98 with a standard error of $0.10.

answer =$2.77 to $3.19

Answer 2

b) Both use the same point estimate of the population mean.

Explain: n=25, mean =2.98, standard error = 0.10

For 90% , z value = 1.645

For 95% , z value = 1.96

C.I => x_bar +- z *(standard error)

So everything is the same except the z value for different confidence levels.

So both use the same point estimate.

Answer 3

c) 

From normal table for 98% conf interval i.e 1 percentile to 99 percentile the Z value is 2.33

==> Confidence interval = μ±2.33σ ==> [2.747 3.213]