Warm-Up Graph each point in the same coordinate plane. 1) A(1,400) 4 minutes 2) B(3,300) 3) C(6,150)4) D(8,50) 5) Suppose that a line were drawn to connect the four points. Would its slope be positive or negative?

1.5 Scatter Plots and Least-Squares Lines 1.5 Scatter Plots and Least-Squares Lines Objectives: Create a scatter plot and draw an informal inference about any correlation between the variables Use a graphics calculator to find an equation for the least-squares line and use it to make predictions or estimates

Scatter Plot Chicken Pox in the United States x y # of years after 1988 Chicken Pox in the U.S. YearReported Cases (in thousands) Reported cases (1000’s)

Correlation x y x y x y positive correlation negative correlation no reliable correlation

Least-Squares Line (line that best fits the data)

Example 1 Create a scatter plot for the data shown below. Describe the correlation. Then find and graph an equation for the least-squares line. x y

Correlation and Prediction x y x y perfect negative correlation perfect positive correlation x y no reliable correlation r = -1r = 0r = 1

Example 2 The table below shows the number of juniors enrolled in Algebra 2 at LHS in six of the last 7 years. The number for the third year has been misplaced. Estimate the number of students enrolled in Algebra 2 in the third year. year #

Homework p.40 #9-11,13,15-20,22 *you need a graphing calculator for this assignment