  Scatterplots show the relationship between two variables. Ex: Temp vs. Test scores, Students vs. lunch cost Gas prices vs. people who drive to work Expenditures 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 movie Hours worked vs. Income Positive Correlation

  As one variable increases, the other variable decreases. Ex: Miles driven vs. gas in tank Temperature vs. number of students who wear jackets Negative Correlation

  There is no relationship between the two variables. Ex: Shoe size vs. IQ Height 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