Scatter Plots and Lines of Fit Use Lines of Fit Example: The table shows the number of students per computer in Easton High School for certain school years from 1996 to 2008. Year 1996 1998 2000 2002 2004 2006 2008 Students per Computer 22 18 14 10 6.1 5.4 4.9 a. Draw a scatter plot and determine what relationship exists, if any. Since decreases as increases, the correlation is negative. y x b. Draw a line of fit for the scatter plot. Draw a line that passes close to most of the points. A line of fit is shown. c. Write the slope-intercept form of an equation for the line of fit. The line of fit shown passes through (1999, 16) and (2005, 5.7). Find the slope. = m = m –1.7 Find in = + b y b. –1.7x 16 = 1993 + –1.7 b ⋅ 3404 = Therefore, an equation of a line of fit is = + 3404. b y –1.7x Exercises Refer to the table for Exercises 1-3. Draw a scatter plot. 1. 1 $5.39 2 $5.66 2. Draw a line of fit for the data. 3 $5.81 3. Write the slope-intercept form of an equation for the 4 $6.03 line of fit. Years Admission Since (dollars) 1999 0 $5.08
Scatter Plots and Lines of Fit Use Lines of Fit Example: The table shows the number of students per computer in Easton High School for certain school years from 1996 to 2008. Year 1996 1998 2000 2002 2004 2006 2008 Students per Computer 22 18 14 10 6.1 5.4 4.9 a. Draw a scatter plot and determine what relationship exists, if any. Since y decreases as x increases, the correlation is negative. b. Draw a line of fit for the scatter plot. Draw a line that passes close to most of the points. A line of fit is shown. c. Write the slope-intercept form of an equation for the line of fit. The line of fit shown passes through (1999, 16) and (2005, 5.7). Find the slope. m = m = –1.7 Find b in y = –1.7x + b. 16 = –1.7 ⋅ 1993 + b 3404 = b Therefore, an equation of a line of fit is y = –1.7x + 3404. Exercises Refer to the table for Exercises 1-3. 1. Draw a scatter plot. 2. Draw a line of fit for the data. 3. Write the slope-intercept form of an equation for the line of fit. Years Since 1999 Admission (dollars) 0 $5.08 1 $5.39 2 $5.66 3 $5.81 4 $6.03