The Professor's Response

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?

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Professor McGukian

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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