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Course Documents
Chapter 1 - Intro
Chapter 2 - Methods for Describing Sets of Data
Chapter 3 - Probability
Chapter 4 - Discrete Random Variables
Chapter 5 - Normal Random Variables
Chapter 6 - Sampling Distributions
Chapter 7 - Confidence Intervals
Chapter 8 - Tests of Hypothesis: One Sample
Chapter 9 - Confidence Intervals and Hypothesis Tests: Two Samples
Sample Exam I: Chapters 1 & 2
Sample Exam II: Chapters 3 & 4
Sample Exam III: Chapters 5 & 6
Sample Exam IV: Chapters 7 & 8
Hello professor, I was doing the new review questions for chapter seven #75 and the result I got for the population proportion interval were 67.12 % and 76.48 %. Your answer says the results are 74.8% and 83.2%, because my Z score for .02/2 = 2.326 my p^= .718 and q^=.282 and my E=.046807. Can you please tell me where is the mistake? I've done the problem 3 times already. Thank you.
Posted to STATS 2 on Monday, September 22, 2014 Replies: 1
Hi Eduardo,
In this problem, it says:
A random sample of 500 students were asked about the costs of traditional textbooks. Three hundred ninety-five of the students stated that traditional textbooks are too expensive. Using the data from the sample, construct a 98% interval estimate of the true proportion of students who believe traditional textbooks are too expensive.
Your sample proportion should be x/n. Here x represents the number of students who think textbooks are too expensive. This will give us 395/500 = 0.79 for p-hat. The q-hat is simply: 1 - 0.79 = 0.21.
That is most likely the source of your error because the rest of your work seems correct. In other words, using your incorrect p-hat and q-hat, I found the answer you found. If you use the correct p-hat and q-hat, you will get the right answer because everything else you did is correct.
Hope that helps,
Professor McGuckian
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