Week 6 Math 225n Statistics Quiz

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.

That is correct!

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.

That is correct!

Answer: ( 0.10, 0.18)

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?

That is correct!

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.

That is correct!