suppose you know and you want an 85% confidence level. What value would you use as z in formula of confidence interval for a population mean? (Round your answer to 2 decimal places.) Value of z a. The sample size is 15 and the level of confidence is 95%. Value of t b. The sample size is 24 and the level of confidence is 98%. Value of t c. The sample size is 12 and the level of confidence is 90%. Value of t Past surveys reveal that 30% of tourists going to Las Vegas to gamble spend more than $1,000. The Visitor's Bureau of Las Vegas wants to update this percentage. a. The new study is to use the 90% confidence level. The estimate is to be within 1% of the population proportion. What is the necessary sample size? (Round your answer to the next whole number.) Sample size b. The Bureau feels the sample size determined above is too large. What can be done to reduce the sample? Based on your suggestion, recalculate the sample size. (Hint: Use an allowable error in the range of 0.01 to 0.05) (Round your answer to the next whole number.) Sample size Forty-nine items are randomly selected from a population of 500 items. The sample mean is 40 and the sample standard deviation 9. Develop a 99% confidence interval for the population mean. (Round your answers to 3 decimal places.) The confidence interval is between and