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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 was looking back through the lecture notes for Chapter 2, examples 16 and 16.5. I was wondering, why when it asks in example 16, (∑xi)², you add whats in the set and then square the sum. But when it asks in example 16.5, is ∑(xi-3)², you square each sum in the set, and then add it all together?

Posted to STATS 1 on Monday, January 20, 2014   Replies: 1


Professor Mcguckian
01/20/2014
7:19 PM EST

Hi Christina,

The difference is that in example 16 this calculation, (∑xi)² has the parenthesis surrounding the summation symbol itself. This means we have to perform the sum as part of what is being done inside the parenthesis. 

In example 16.5, this calculation, ∑(xi-3)² does not have the summation symbol inside of the parenthesis. What is inside the parenthesis is done first, then we perform the summation. 

Hope that clears it up,

Professor McGuckian

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