Standard:MAFS.8.SP.1.2 CREATING A LINEAR MODEL Know that straight lines are widely used to model relationships between two quantitative variables. For scatter plots that suggest a linear association, informally fit a straight line, and informally assess the model fit by judging the closeness of the data points to the line.

Warm Up A.(6, 15) B.(6, 9) C.(8, 12) D.(9, 7) E.(10, 12) F.(12, 15) Graph the following points on the coordinate grid

Answer to Warm-Up

Vocabulary Scatter Plot Positive and Negative Correlation Line of Best Fit

Scatter Plot A scatter plot is a graph of a collection of ordered pairs. The graph looks like a bunch of points. The points show the relationship between two sets of data. The points on the graph can move in a general direction.

Positive Correlation We call it a positive correlation when both the x-coordinates and the y- coordinates increase simultaneously.

Positive Correlation The more hours the person worked, the higher the income. Both x and y are increasing simultaneously. Hours worked daily Income (in dollars)

Negative Correlation We have a Negative Correlation when one variable is increasing and the other is decreasing. In this case the graph goes downhill. x y

Negative Correlation Temperature Outside Heating Bill

No Correlation The points are scattered. There is no pattern. The points are not related There is no correlation

No Correlation

Recap Identify the correlation below. Label as positive, negative or no correlation. _____________ 12 3

Line of Best Fit The line of best fit is the straight line that best represents the data on a scatter plot. may pass through all of the points, some of the points, or none of the points. can be used to make predictions as to what can happen if the trend continues. represents a relationship between two quantities.

Lines of Best Fit

Guided Practice Years of experience Income (hourly wage) Hours Watch TV Test Score

Answer to Guided Practice

Independent Practice Time in after school (weekly) Test scores (average) Label the x and y axis 2.List the ordered pairs 3.Plot the ordered pairs 4.Is there a correlation in the data? 5.Is it positive or negative or no correlation 6.Draw the line of best fit

Independent Practice (0,60), (1,65), (2,70), (3,75), (4,80), (5,90) The more time spent on activities, the higher the test scores. It is a positive correlation.