7.1 Draw Scatter Plots & Best-Fitting Lines 7.1 HW Quiz: Friday 7.1, 7.2 Quiz: TBA 7.1, 7.2, 7.7 Test: Sept. 22 Make-up work needs to be made up by Monday afternoon! Need: Graphing Calculator

Vocabulary Scatter plot: a graph of a set of data pairs (x, y) Positive correlation: y tends to increase as x increases Negative correlation: y tends to decrease as x increases

More Vocabulary Correlation coefficient: denoted by r, is a number from -1 to 1 that measures how well a line fits a set of data pairs (x, y). If r is near 1, the points lie close to a line with a positive slope. If r is near 1, the points lie close to a line with a positive slope. If r is near -1, the points lie close to a line with a negative slope. If r is near -1, the points lie close to a line with a negative slope. If r is near 0, the points do not lie close to any line. If r is near 0, the points do not lie close to any line.

Correlation Coefficient: What do you think the correlation coefficient would be for these graphs? x y x y x y x y x y

If “r” is…

Guided Practice for Ex.1, p. 248 For each scatter plot, (a) tell whether the data have a positive, negative, or approximately no correlation, and (b) tell whether the correlation is closest to -1, -0.5, 0, 0.5, or 1. 1)2)

More Vocabulary Best-fitting line: line that lies as close as possible to all the data points Linear regression: a method for finding the equation of the best-fitting line, or regression, which expresses the linear relationship between the independent variable x and the dependent variable, y, e.g. y = ax + b

Example 2: Approximate the best-fitting line Scatterplot Best-Fit Line EQ Best-Fit Line Graph See Handout

Guided Practice for Example 2: p. 249 Draw a scatter plot and approximate the best-fitting line for the following data: (1, 22), (2, 30), (3, 33), (4, 39), (5, 45) y = 5.5x

Start Homework NOW! P #1-2, 7-9 (may use graphing calculator) Finish PSAT Practice WS Finish PSAT Practice WS will turn in tomorrow! (show work!)