Stats200_week_5 homework A++ USE AS A GUIDE ONLY

Why is a 99% confidence interval wider than a 95% confidence interval?

Solution) 

12. A person claims to be able to predict the outcome of flipping a coin. This person is correct 16/25 times. Compute the 95% confidence interval on the proportion of times this person can predict coin flips correctly. What conclusion can you draw about this test of his ability to predict the future?

15. You take a sample of 22 from a population of test scores, and the mean of your sample is 60.

(a) You know the standard deviation of the population is 10. What is the 99% confidence interval on the population mean?

 Solution)

(b) Now assume that you do not know the population standard deviation, but the standard deviation in your sample is 10. What is the 99% confidence interval on the mean now?

You were interested in how long the average psychology major at your college studies per night, so you asked 10 psychology majors to tell you the amount they study. They told you the following times: 2, 1.5, 3, 2, 3.5, 1, 0.5, 3, 2, 4.

(a)                Find the 95% confidence interval on the population mean.

100. What is meant by the term “90% confident” when constructing a confidence interval for a mean?

a. If we took repeated samples, approximately 90% of the samples would produce the same confidence interval.

b. If we took repeated samples, approximately 90% of the confidence intervals calculated from those samples would contain the sample mean.