A survey of 25 randomly selected customers found the ages shown (in years). The mean is 33.16 years and the standard deviation is 9.89 years. a) Construct a 99% confidence interval for the mean age of all customers, assuming that the assumptions and conditions for the confidence interval have been met. b) How large is the margin of error? c) How would the confidence interval change if you had assumed that the standard deviation was known to be 10.0 years? 47 48 22 26 450 29 34 39 25 35 33 34 43 11 26 37 27 33 37 28 30 44 46 a) What is the confidence interval? (Round to two decimal places as needed.) b) What is the margin of error? The margin of error is. (Round to two decimal places as needed.) c) What is the confidence interval using the given population standard deviation? Select the correct choice below and fill in the answer boxes within your choice. (Round to two decimal places as needed.) O A. The new confidence interval (. ) is wider than the interval from part a. O B. The new confidence interval ( is narrower than the interval from part a.

1. A recent study of 22 motorists showed that they spent an average of P750 per week. The standard deviation of the sample was P90. Find the 99% confidence interval of the true mean. Solution: 2. A sample of 15 National Collegiate Athletics Association (NCAA) basketball players had an average height of 6 feet with a sample standard deviation of 0.80 foot. Find the 90% confidence interval of the true mean height of all players. Solution:

A random sample of 500 observations yields x̅ =400 and s=50. What is the  95% confidence interval for the population mean?

A random sample of 10 children found that their average growth for the first year was 9.8 inches, with a standard deviation of 0.96 inches. Find the 85% confidence interval of the mean growth of all American children in the first year of life.What is the name of the confidence interval?

Suppose we have data coming from 69 i.i.d) observations. The sample mean is JÓ28 and the sample standard deviation is calculated to be 1.63. Find a 95% confidence interval for the true mean.

a researcher wishes to develop an interval estimate for response scores on user surveys. She's not sure about the standard deviation, but in previous years the scores have ranged from 25 to 86. How large a sample should she draw if she wants to construct a 95% confidence interval level that will be within 3 points of the population mean score?

A random sample of 64 shoppers showed that they spend an average of $27.31 per visit at the Sunday Mornings Bookstore. The standard deviation of the population is $2.14. Find the 90% confidence interval of the true mean. Please include all work showing how you found your answer.

If n=22, (x-bar)=34, and s=17, construct a confidence interval at a 99% confidence level. Assume the data came from a normally distributed population. Give your answers to one decimal place.