Tonight please complete the following in your textbook (or below):
Page 446: 7bc, 14, 23d, 33
- Be sure to practice "interpreting the confidence level" in #'s 14c and 23d!
- Remember to check the conditions for 14a--you need to do the full confidence interval process!
Here are the book problems for tonight's hw:
And here are the answers so you can check:
- 7b.) True
- 7c.) True (larger samples mean a smaller standard deviation--so if the margin of error is fixed, and standard deviation goes down, our confidence level/z* must increase to maintain a fixed ME)
- 14a.)
- Conditions:
- This is a random sample of 1000 people from the mailing list.
- 1000 is less than 10% of all people on the mailing list
- (1000)(0.123)>10 and (1000)(0.877) > 10
- OR... 123 > 10 and 877 > 10
- Math:
- 0.123 +/- 1.645sqrt(0.123x0.877/1000) = (10.6%, 14.0%)
- 14b.) = Interpret:
- We are 90% confident that the true percentage of people the company contacts who may buy something falls between 10.6% and 14% based on this sample of 1000 people from the mailing list.
- 14c.) Approximately 90% of confidence intervals based on samples of 1000 people will contain the true % of people the company contacts who may buy something.
- 14d.) The confidence interval suggest that a mass mailing WILL be cost-effective because the interval suggest that the mailing produces a return greater than 5%--this is because our entire interval is above 5%.
- 23d.) About 95% of confidence intervals created using samples of 226 college students will contain the true proportion of students nationwide who are only children.
- 33.) Solve the equation: 0.02 = 1.96sqrt((0.25x0.75)/n)
- n = 1801 people
- *If used p-hat = 0.5 you should get n = 2401 people
Tomorrow in class we'll start with a stamp; then we'll work in groups on some AP Free Response, we'll score them, and then look at 3 AP MC--this is all in preparation for a quiz on Wednesday! Then, after Wednesday's quiz it's on to hypothesis tests! See you tomorrow!
No comments:
Post a Comment