Scatterplots

Scatterplots show the relationship between

two variables.Ex: Temp vs. Test scores, Students vs. lunch costGas prices vs. people who drive to workExpenditures vs. Profit

Scatterplots

Correlation is the relationship between two

variables.

Correlation can come in three forms: Positive Correlation Negative Correlation No Correlation

Correlation

As one variable increases, the other variable

increases as well.

Ex:Movie tickets sold vs. Profit from movieHours worked vs. Income

Positive Correlation

As one variable increases, the other variable

decreases.

Ex:Miles driven vs. gas in tankTemperature vs. number of students who wear jackets

Negative Correlation

There is no relationship between the two

variables.

Ex:Shoe size vs. IQHeight vs. Test scores

No Correlation

Best fit lines are used to represent the data

collected and make predictions about future events.

NEVER CONNECT THE POINTS IN A SCATTERPLOT.

Lines of best fit should roughly cut data in half.

Lines of Best Fit

The purpose of a line of best fit is to

accurately (as possible) make predictions based on past events.

We don’t use old data to make a prediction.

For example: Just because you studied for 15 minutes and received a 90% does not mean every time you study 15 minutes you will receive a 90%.

Lines of Best Fit

There are some ways to see if a line of best fit

is appropriate for a set of data:

Check the y-intercept-is it too high or too low?

Check the slope-does it match the correlation? Positive slope = positive correlation Negative slope = negative correlation

Lines of Best Fit

Scatterplots Worksheet #1

Homework