The owner of a currency exchange bureau on an airport wishes to estimate the mean value of cash necessary for the exchange of PLN and EUR. Experience tells the owner that the demand for euro is distributed normally, with a standard deviation equal to 4 (thousand PLN). Having observed the demand for 10 days, the owner obtained a mean of 24.4 ( thousand PLN). Calculate the realization of the confidence interval for the expected demand with a confidence level of 0.90.

Question of the day. The mean weekly sales of the chocolate bar in candy stores was 146-3 bars per store. After an advertising campaign the mean weekly sales in 22 stores for a typical week increased to 153-7 and showed a standard deviation of 17-2. Was the advertising campaign successful?

A sample of 21 minivan electrical warranty repairs for “loose, not attached” wires (one of several electrical failure categories the dealership mechanic can select) showed a mean repair cost of $45.66 with a standard deviation of $27.79. (a) Construct a 95 percent confidence interval for the true mean repair cost. (b) How could the confidence interval be made narrower? (Data are from a project by MBA student Tim Polulak.)

7. It is well known that car buyers often add accessories to their new cars. A sample of 179 Ottawa purchasers yielded a sample mean of $5000 worth of accessories added to the purchase above the base sticker price. Suppose the cost of accessories purchased for all Ottawa has a standard deviation of $1500. (a) Calculate a 95% confidence interval for the average cost of accessories on Ottawa. - Section Break - (b) Determine the margin of error in estimating the average cost of accessories on Ottawa. (c) What sample size would be required to reduce the margin of error by 50%?

A magazine conducts an annual survey in which readers rate their favorite cruise ship. All ships are rated on a 100-point scale, with higher values indicating better service. A sample of 33 ships that carry fewer than 500 passengers resulted in an average rating of 85.59, and a sample of 44 ships that carry 500 or more passengers provided an average rating of 81.40. Assume that the population standard deviation is 4.55 for ships that carry fewer than 500 passengers and 3.97 for ships that carry 500 or more passengers. A) What is the point estimate of the difference between the population mean rating for ships that carry fewer than 500 passengers and the population mean rating for ships that carry 500 or more passengers? (Use smaller cruise ships − larger cruise ships.)   (b) At 95% confidence, what is the margin of error? (Round your answer to two decimal places.)   (c) What is a 95% confidence interval estimate of the difference between the population mean ratings for the two sizes of…

Tom wants to estimate the percentage of students who live more than 3 miles from the school.He wants to create a 95% confidence interval which has a margin of error of at most 3% .How many students must be polled to create the confidence interval?

Suppose that the average student buys 12 books a year. You have a theory that by offering a discount you can increase that number. You run a pilot project by offering the discount to a random sample of 25 students and you find that x = 14 and s = 4.32 State the null and alternative hypotheses Give the first symbol in the expression for Ho