# Mystery Number: What Does it Tell Us?

- Author:
- Tim Brzezinski, GeoGebra Team

- Topic:
- Algebra, Correlation, Linear Regression

## Shown below is is a list of points. Note the mystery number "r" changes as you move them. Drag them around for a bit. As you do, pay attention to the value of this mystery number.

What do you notice? What do you wonder? List any observations you see below.

## If possible, move these points around to make the value of "r" as high as you possibly can. Then answer the question that follows.

Is there a maximum possible value for * r* ? If so, what is it?

## If possible, move these points around to make the value of "r" as low as you possibly can. Then answer the question that follows.

Is there a minimum possible value for * r* ? If so, what is it?

## Is it possible to get r = 0? Try it!

## Can you get r = 0 in a way different from above? Try it!

What exactly does this value ** r **tell us? How would you describe it?
Describe as best as you can in your own words.