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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

Is it safe to assume that in HW: 9.5, where The Goverment's mean is 35.50 and the Private is 54.6, that the final interval is going to be negative. (This could be in any situation) Per say if Goverment mean is 54.6 and 35.50 that the final interval is positive ?

Posted to STATS 2 on Thursday, October 17, 2013   Replies: 2


Professor Mcguckian
10/17/2013
4:25 PM EST

Hi Andrea,

No, you can't assume the interval will be all positive or all negative just by looking at the sample means.  The first reason is that it depends on how you set up the subtraction in the interval. The second reason is that there may not be a significant difference between the two means in question. In that case, you will get an interval that is both negative and positive. 

There is no way to avoid actually calculating the confidence interval to determine if there is a significant difference between the means.

Hope that answers your question,

Professor McGuckian


.
10/17/2013
5:03 PM EST
Thank you for your help!

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