# suppose you know σ and you want an 85% confidence level. What value would you use as z in formula of

 suppose you know σ 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 [removed]

 a. The sample size is 15 and the level of confidence is 95%.

 Value of t [removed]

 b. The sample size is 24 and the level of confidence is 98%.

 Value of t [removed]

 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 [removed]

 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 [removed]

 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   [removed] and [removed]