Pre Algebra ( Period 1)

Scatter Plots 8-5 & 8-6

CORRELATION GRAPHS: SCATTER PLOTS
USES SOMETHING YOU ALREADY KNOW: (x, y) graphing

Scatter plots are graphs that show the RELATIONSHIP between 2 SETS OF DATA
This type of graph is used for surveys

For example, you survey students about how long they study and what grade they received

You survey people about how many hours they use their heaters in relation to the temperature outside.

CORRELATION = relationship

There are 3 types of correlations:

1) POSITIVE - the two sets of data travel in the SAME DIRECTION

The scatter graph looks like it's going up from left to right
(as one increases, so does the other or as one decreases, so does the other)

Ex) The amount of time spent studying and their grades

2)NEGATIVE - the two sets of data travel in OPPOSITE DIRECTIONS

The scatter graph looks like it's going down from left to right
(as one increases, the other decreases or vice versa)

Ex) As the temperature increases, the use of heaters decreases

3) NO CORRELATION - the two sets have no relationship to each other

The scatter graph is all over the place

Ex) Your math grade and the temperature outside

LINE OF BEST FIT: If the data has a correlation (either positive or negative), you will be able to draw a line that "fits" the data. It may not actually go through any of the specific data points, but it will be in the center of most of the data.

This line is a TREND LINE and can be used to make projections or analytical statements