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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

Hi Professor,

I am reviewing the examples on Chapter 8 and got stuck on something.
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Example 122: In a 2007 study of different popular diets, 77 people used a modified* version of the
Atkins Diet for one year. Their mean weight change was -10.34 lbs.
Assume that the population standard deviation for all such weight
changes is known to be 15.51 pounds. Use a significance level of
0.05 to test the claim that the mean weight change is equal to zero.
Does the diet seem to be effective? Does the mean weight change
seem substantial enough to justify the diet? What assumptions are
necessary for the test we just conducted to be valid?
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The claim is: m=0 but why is it the null hypothesis and not the alternative hypothesis? I assumed when we test a claim it's going to be the alternative hypothesis and the opposite would be the null.

Posted to STATS 1 on Monday, December 8, 2014   Replies: 1


Professor Mcguckian
12/08/2014
11:22 PM EST

Hi Lina,

The claim can be either the null or the alternative hypothesis. It all depends what symbol is used in the claim. If the claim features any kind of an equal sign (≥ , ≤, or =), it is the null hypothesis.

Professor McGuckian

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