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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

Ask the Professor Forum

Hiii Professor

I was wondering if you could tell me why in question #32 in chapter 9 are the signs not equal? I don't know if I'm reading it wrong, or maybe I'm not understanding

Posted to STATS 2 on Tuesday, October 14, 2014   Replies: 2

Professor Mcguckian
11:38 PM EST

Hi Sandra,

Here is the key sentence to determine the claim, "Use the results below and a 2% significance level to test the claim that the program produces some change in the student’s ability to spot errors in written work."

If the program did not produce a change in the student's ability, you would say the before and after means are equal wouldn't you? You would have to because no change would mean the before and after are the same. This claim doesn't say there will be no change, it says there will be a change. Thus, the the mean before is not the same as the mean after (i.e., µbefore ≠ µafter). "Some change," does not imply an improvement necessarily, so don't make the mistake of assuming the change has to be for the better.

Hope that helps,

Professor McGuckian

7:54 AM EST
Thank you!

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