Work doesn’t need to be shown.
1) Find the Z(α/2) for a 95% confidence interval.
Your answer should be a positive decimal rounded to the hundreths place.
2)The math scores for a sample of 100 eighth graders had a mean of 80 with a sample standard deviation of 9. What is the best point estimate for the estimate of the population mean of the math scores for all eighth graders?
3)A California State Lottery official wishes to estimate the average amount of money that a person in the State of California who plays the lottery spends on Lottery tickets in a given month. He wants to be 90% confident in his estimate. He randomly samples 150 people who play the California State Lottery and finds that for this sample the average amount spent is $ 39.50 with a sample standard deviation of $3.50. What is the lower boundary of the confidence interval estimate to the nearest penny? Please use a dollar sign in expressing your answer to the nearest cent.
4)A statistics student would like to estimate the average age of students at her college. She would like to be 85% confident that her estimate includes the actual college population mean. She did a smaller preliminary survey and found that a reasonable estimate of the population standard deviation was 4 1/2 years. How many people must she survey if she wants to be within 1/2 year of the true population mean?(Do not use any commas in your answer)
5)Find the t(α/2) for a 99% confidence interval based on a sample size of 20.
Use the t – distribution table to find this value to the thousandth decimal place.
6)A researcher is conducting a study about the average amount of tire tread wear for cars on the road today. The tread depth of the left front tire is measured in 28 randomly selected cars on the road today. The sample mean was found to be .30 inches and the sample standard deviation was found to be .03 inches. Find the 90% confidence interval estimate for the average amount of tire tread wear based on this sample. Assume that the variable is normally distributed.
Give your answer as the interval defining values in ascending order separated by a comma.
For example .53,.51 DO NOT USE Parentheses Round the answers to the hundredth decimal place.
10)In a local school district it was found that in a random sample of 550 students, 285 of those students brought their own lunch to school. What is the Margin of Error for the 95% confidence interval estimate for the true percentage of students who bring their lunch to school. Answer as a percent rounded to the nearest tenth.
11)A political pollster wishes to estimate the percentage of female voters who believe in a “Woman’s Right to Choose”. He wants to be 98% confident that his estimate is within 3% of the true population percentage of female voters who believe in a “Woman’s Right to Choose”. What is the minimum number of female voters that this political pollster need to sample randomly in order to accomplish this task? Round your answer “up” to the nearest counting number. Do not use any commas in your answer.
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