Read pages 154-161 (up to the section on “Straightening”). From the exercises on pages 168-173, do 9, 10, 14, 15, 41, 42.

There will be a **reading quiz** about this section in class tomorrow, and we will have a more thorough, though short, quiz on chapter 6 on **Friday, October 6**.

Also, check out Guess the Correlation, a surprisingly addictive online game where you, surprise, surprise, guess the correlation value for a randomly created association. How high can you get your score?

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I don’t understand why you can know the strength by averaging the sum of products. And I wonder how to prove r is between -1 and 1. I searched online but I don’t understand how they use the vector to explain this.

Hi Yirui-

This is a great question, and I don’t have a great answer for it right now. I promise I’ll look into this and try to get back to you.

Mr. Kirk

Thank you

Hi again Yirui-

I’ve done some research and I think I’ve come with some acceptable answers to your questions. I’m going to be discussing them in two posts on my website. You can see the first one here: https://mrkirkmath.com/2017/10/05/mathematical-musing-what-is-r/