Chamberlain College of Nursing Math 225N Statistics Quiz Week 6

Question 1

A statistics professor recently graded final exams for students in her introductory statistics course. In a review of her grading, she found the mean score out of 100 points was a x¯=77, with a margin of error of 10.

Construct a confidence interval for the mean score (out of 100 points) on the final exam.

Answer: (67, 87)

Question 2

A random sample of adults were asked whether they prefer reading an e-book over a printed book. The survey resulted in a sample proportion of p′=0.14, with a sampling standard deviation of σp′=0.02, who

preferred reading an e-book.

Use the empirical rule to construct a 95% confidence interval for the true proportion of adults who prefer e- books.

Question 3

The pages per book in a library are normally distributed with an unknown population mean. A random sample of books is taken and results in a 95% confidence interval of (237,293) pages.

What is the correct interpretation of the 95% confidence interval?

We estimate with 95% confidence that the sample mean is between 237 and 293 pages.

We estimate that 95% of the time a book is selected, there will be between 237 and 293 pages. We estimate with 95% confidence that the true population mean is between 237 and 293 pages.

Question 4

The population standard deviation for the heights of dogs, in inches, in a city is 3.7 inches. If we want to be 95% confident that the sample mean is within 2 inches of the true population mean, what is the

minimum sample size that can be taken? Round up to the nearest integer.

Answer: 14 dog heights

Question 5

Clarence wants to estimate the percentage of students who live more than three miles from the school. He wants to create a 98% confidence interval which has an error bound of at most 4%. How many students should be polled to create the confidence interval?

z0.10  z0.05  z0.02

5

z0.01 z0.005

1.28

1.64

1.96

2.32

2.57

    2       5       0       6       6   

Use the table of values above.