# Scatter Diagrams Objective: Draw and interpret scatter diagrams. Distinguish between linear and nonlinear relations. Use a graphing utility to find the.

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Scatter Diagrams Objective: Draw and interpret scatter diagrams. Distinguish between linear and nonlinear relations. Use a graphing utility to find the line of best fit.

Terms Relation Correspondence between two sets Dependent variable : y the value of y is determined by the value of x Independent variable : x Scatter diagram Plot the ordered pairs using rectangular coordinates.

Linear data To determine if data is linear Graph the data Does the data have a general pattern of increasing or decreasing? Look on page 201: can you see the “linear” pattern in those graphs stated as being linear? Do you see that those marked “nonlinear” do not have this pattern?

Finding a Linear Regression (Line of Best Fit) 1. Graph the data 2. Draw a line through the data 3. Identify two points on the line drawn through the data. (These points may or may not be data points.) 4. Find the equation of the line using the points selected. 1. Find slope 2. Find y-intercept 3. Write equation

Using a calculator Go to STAT mode Select EDIT Clear old data Input new data Quit Go back to STAT mode Select CALC Select LinR The calculator will give you the slope and y- intercept. Use these values to write the equation.

Know your calculator a: slope or y-intercept depending on the calculator b: slope or y-intercept depending on the calculator corr: value showing how well the equation describes the data -1: perfect linear pattern going down 1: perfect linear pattern going up 0: no linear pattern Closer the “correlation coefficient” is to -1 or 1 the better the fit of the line. n: number of data values inputted into calculator

Assignment Page 204 #5, 7, 9, 13, 15, 17, 19

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