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ASK THE PROFESSOR FORUM

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

Ask the Professor Forum

I also had a question on section 7.6 number 62.

Posted to STATS 1 on Saturday, November 23, 2013   Replies: 1


Professor Mcguckian
11/30/2013
3:42 PM EST

Hi Natalie,

In this problem, we need to use the margin of error formula for the confidence interval for proportion to find an equation for n. That part is straightforward. However, the second part is not so easy.

We need to find values for p-hat and q-hat that when multiplied produce a maximum. This might remind you of those word problems from Algebra that read, "Find two numbers that sum to 1 and have a product that is a maximum..." In the video below, I have walked you through how that is done, but it is not something I would ask you to do on an exam. For these proportion, sample-size problems, we assume p-hat and q-hat are both 0.5. The video just explains why that is the case.

Professor McGuckian

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