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# Equation of the best fit line

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- Lesson: 3b6:41

### Equation of the best fit line

#### Lessons

• $a=\frac{n\sum xy-\sum x \sum y}{n\sum x^2-(\sum x)^2}$

• $b=\overline{y}-a\overline{x}$

- Introduction

• Formula for the Best Fit Line

• What are Residuals? - 1.
**Determining the Equation for a Best Fit Line**

Given the following bivariate data give the equation for the best fit line and plot it on the given graph.

__x____y__1

2

2

2

3

4

4

5

- 2.
**Determining the Equation for a Best Fit Line using Calculator Commands**

For the following bivariate data:

__x____y__1

9

2

7

3

8

4

5

5

5

6

3

7

2

a)Using a graphing calculator plot the points on a graphb)Still using your graphing calculator find the equation for the best fit line and plot it on the same graph - 3.
**Interpretation graphical Data**

In Skyrim (a video game) I plotted what level I was when I killed my first 5 dragons. The graphical data is given below:

__# of dragons killed____Corresponding level__1

Level 4

2

Level 5

3

Level 6

4

Level 6

5

Level 7

a)What is the sum of all the residuals squared?b)Using the data above extrapolate what my level will be when I kill my 8th dragon. Is this a good estimation? Why or why not?