Scatter Plots

Scatter Plots

• Scatter Plot – a graph of ordered pairs

on a coordinate plane that shows the
relationship between a set of data
with two variables.

Scatter Plots and Lines of Fit

Positive correlation

Negative Correlation

Correlation Coefficient

Correlation Coefficient

No correlation

Multiple Choice

Which correlation coefficient shows a strong negative relationship?

• -0.9

• -0.09

• 0.8

• -.03

Multiple Choice

If the Correlation Coefficient is 0.2 it is

• weak and negative

• weak and positive

• strong and positive

• strong and negative

• no correlation

Lines of Fit

When the data points all lie close to a line we can

draw a line of fit to show the trend in the data.

Steps:
1.

Make a scatter plot and determine if a relationship
exists.

2.

Draw a line that seems to pass close to most of the data
points.

3.

WRITE THE EQUATION OF THE LINE
Use two points on the line of fit to write an equation for
the line.

MCAS

Examples

Multiple Choice

MCAS

• A

• B

• C

• D

Multiple Choice

• A

• B

• C

• D

Multiple Choice

• A

• B

• C

• D

Multiple Choice

• A

• B

• C

• D

Choose the point (1, 151) and (8, 230)

To write our equation we must first find

the slope m = y2 – y1

x2 – x1

M = 230 – 151

8-1

Now we know the slope and a
point so we can use point slope
form: y – y1 = m (x- x1)

Y – 151 = 11.3 (x – 1)

“predict the drop of a roller coaster 30
years after 1988”

Y – 151 = 11.3 (30-1)
Y – 151 = 11.3 (29)
Y – 151 = 327.7
Y= 428.7

So, 30 years after 1988 the drop of the
roller coaster would be about 429 feet.

Multiple Choice

Which equation best represents the scatterplot shown?

• y=1/3x+2

• y=1/2x+2

• y=1/2x+1

• y=2x+2