Thursday HW

Tonight you have two responsibilities for HW:

1.) Complete the "bottom left slide" provided in class today (or below)--this was posted yesterday, so you may have it done already! If so, nice job!

• FULL interval process (conditions, math = calculator screen and formula, interpret interval)

2.) Please also complete the following in your textbook:

Pages 446-448: 11, 37

• For 11b don't stress too much, try to explain what ME means and then use the answer in the back of the book to help you understand this idea
• The concept in 11e will be one of the main concepts we address in class tomorrow--you got this!
• For 37--more math! All math here! Set up a formula using the given margin of error, solve for z*, and then use this to determine the confidence level!
• C. Level = normalcdf(-z*, +z*, 0, 1)

Weekend HW (if you want to get a head start)!

• Pages 446-448: 7, 8, 13abd, 27a, 31ac, 33, 37, 38a
• For 31ac....
• What do you notice--how much larger of a sample did we need to cut the margin of error in half (from 6% to 3%)?
• How could you have answered (c) without using the "finding n" formula?
• For 38a, "explain why the poll is actually inconclusive" means "explain why we cannot conclude that the amendment will win" (based on this poll and confidence interval)

Today's Class Recap (stupid delay shortening class):

• Stamp = pop classwork assignment! (if you were out today you will do this tomorrow)
• Ch. 19 Notes: the CI formula and the AP formula sheet
• Margin of Error
• How do we calculate margin of error (ME)? (middle left slide)
• What is margin of error? (definition)
• How can we use a given sample statistic and ME to create a confidence interval?
• Intro to Finding N
• How can we use a given ME to find sample size? (bottom right slide)

"Bottom Left Slide" (tonight's HW) Answer Key:

• Conditions:
• We will assume this is a random sample of 2,002 25-32 year old Americans.
• 2,002 is less than 10 % of all 25-32 year old Americans
• (2002)(0.53) > 10   and   (2002)(0.47) > 10
• A one proportion z-interval is appropriate.

• Math:
• One Prop Z Int:
• (0.50124, 0.5587) = 0.53 +/- 2.576 sqrt(0.53 x 0.47 / 2002)
• p-hat = 0.53
• n = 2,002
• x = (0.53)(2002) =1061

• Interpret:
• We are 99% confident that the true percentage of all employed 25-32 year old Americans with a bachelor's degree who are "very satisfied" with their current job falls between 50.124% and 55.87% based on this sample of 2002 25-32 year olds.