# Lines of best fit

#### Phobosdeimos

##### New member
The average annual exchange rate in Canada for the US Dollar from 1998-2007 is shown in the following table. Draw a scatter plot, without using graphing technology

Year Exchange Rate
1998 .67
1999 .67
2000 .70
2001 .74
2002 .80
2003 .81
2004 .86
2005 .87
2006 .90
2007 .99

To determine the Slope I did the following
1998 - 2006 = -8
.67 - .90 = -.23

y= .23
Divide
x = -8

The slope of the line is - 0.02875

I then tried the y intercept
y = mx +b

.90 = - 0.02875 (2006) + b

.90 = -57.6725 + b

.90
- 57.6725 = b

b = 58.5725

This is what I came up for the y Intercept (58.5725)

Doesn't seem right to me

Phobos

#### Sudharaka

##### Well-known member
MHB Math Helper
The average annual exchange rate in Canada for the US Dollar from 1998-2007 is shown in the following table. Draw a scatter plot, without using graphing technology

Year Exchange Rate
1998 .67
1999 .67
2000 .70
2001 .74
2002 .80
2003 .81
2004 .86
2005 .87
2006 .90
2007 .99

To determine the Slope I did the following
1998 - 2006 = -8
.67 - .90 = -.23

y= .23
Divide
x = -8

The slope of the line is - 0.02875

I then tried the y intercept
y = mx +b

.90 = - 0.02875 (2006) + b

.90 = -57.6725 + b

.90
- 57.6725 = b

b = 58.5725

This is what I came up for the y Intercept (58.5725)

Doesn't seem right to me

Phobos
Hi Phobosdeimos,

The question tells you to draw a scatter plot according to the given data. Your slope and y-intercept is for the straight line that goes through the two points $(1998, 0.67)$ and $(2006, 0.90)$. If the points given approximately lie on a straight line you can find the best fitting straight line using linear regression as below.

Introduction to Linear Regression