Line of Best Fit The line of best fit is the line that lies as close as possible to all the data points. Linear regression is a method for finding the equation of the regression line, Remember:
Line of Best Fit On Graphing Calculator First press STAT and 1:EDIT. Enter the x- and y- coordinates in your calculator under L1 and L2. Then hit STAT, CALC, and arrow down to 4: LinReg (ax+b) and Press ENTER Should say xlist: L1 ylist: L2 Hit ENTER 5 times Arrow down and “a” is the slope of the line of best fit, “b” is the y-intercept
Ex. 1. The table shows the cost of a catered lunch buffet for different numbers of people. Find the LOBF for the data. # of people 12 18 24 30 36 42 Costs 192 288 384 480 576 672 a = 16 b = 0 y = 16x
2. Ex: The table gives the average class score y on each unit test for the first 6 units of CRM. Approximate the best fitting line for the data. x 1 2 3 4 5 6 y 84 83 86 88 87 90 a = 1.3 b = 81.9 y = 1.3x + 81.9 If the trend continues, what would be the average score on the 8th unit exam? (This is called extrapolation)
3. Ex: The ordered pairs (x, y) give the height y in feet of a young tree x years after 2000. Approximate the best fitting line for the data. (0,5.1), (1,6.4), (2,7.7), (3,9), (4,10.3), (5,11.6), (6,12.9) a = 1.3 b = 5.1 If the trend continues, what would be the height of the tree after 9 years?
4. Ex: The table below gives the number of people y who attended each of the first seven football games x of the season. Approximate the best-fitting line for the data. x 1 2 3 4 5 6 7 y 722 763 772 826 815 857 897 a = 27 b = 699.4 If the trend continues, what would be number of people attending the 10th game?
Remember y= mx + b This is slope-intercept form of a line. Remember slope can be positive or negative. Remember that b tells the y-intercept (where the line crosses the y-axis)
5. Which of the following could be a line of best fit for the following scatter plot? y = 1.5x + 19 y = 1.5x – 19 y = -1.5 + 19 y = -1.5 – 19
6. Which of the following could be a line of best fit for the following scatter plot? y = -16.7x + 18.9 y = -16.7x +18.9 y = 16.7 + 18.9 y = 16.7 – 18.9
7. Which of the following could be a line of best fit for the following scatter plot? y = 6.7x – 57.9 y = 6.7x + 57.9 y = -6.7 + 57.9 y = -6.7 – 57.9