Find the critical value z Subscript c necessary to form a confidence interval at the level of confidence shown below.
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Find the critical value z Subscript c necessary to form a confidence interval at the level of confidence shown below.
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A random sample of 75 eighth grade students’ scores on a national mathematics assessment test has a mean score of 278. This test result prompts a state school administrator to declare that the mean score for the state’s eighth graders on this exam is more than 275. Assume that the population standard deviation is 36. At alphaequals0.12, is there enough evidence to support the administrator’s claim? Complete parts (a) through (e).
russellc, , Statistics, 0
see excel spreadsheet. This your answer

In a survey of 641 males ages 1864, 394 say they have gone to the dentist in the past year. Construct 90% and 95% confidence intervals for the population proportion. Interpret the results and compare the widths of the confidence intervals. If convenient, use technology to construct the confidence intervals. The 90% confidence interval for the population proportion p is The 95% confidence interval for the population proportion p is Interpret your results of both confidence intervals. Which interval is wider?
russellc, , Statistics, 0 


Use the confidence interval to find the margin of error and the sample mean.
russellc, , Statistics, 0
(0.264,0.460) The margin of error is 0.098.The sample mean is .3620.

A credit card company claims that the mean credit card debt for individuals is greater than $ 5000. You want to test this claim. You find that a random sample of 30 cardholders has a mean credit card balance of $ 5202 and a standard deviation of $ 600. At alpha equals 0.01, can you support the claim? Complete parts (a) through (e) below. Assume the population is normally distributed.
russellc, , Statistics, 0
see excel spreadsheet. This your answer

You are given the sample mean and the population standard deviation. Use this information to construct the 90% and 95% confidence intervals for the population mean. Interpret the results and compare the widths of the confidence intervals. If convenient, use technology to construct the confidence intervals. A random sample of 60 home theater systems has a mean price of $140. Assume the population standard deviation is $15.40 Construct a 90% confidence interval for the population mean. The 90% confidence interval is (nothing,nothing).
russellc, , Statistics, 0