Lines of Best Fit #1 When data show a correlation, you can estimate and draw ____________________ that approximates a trend for a set of data and use it to make predictions. Line of Best Fit: a ___________ line that comes closest to the points on a scatter plot. Steps for Drawing the Line of Best Fit: 1.) Plot the data as ordered pairs – make a scatter plot. 2.) Study the points to see if there is a relationship between the 2 sets of data – positive, negative, or no association (see Data Relationships slide).

#2 Data Relationships There are three ways to describe data displayed in a scatter plot and the adjectives “strong” and “weak” can also be used to further define the association. _______ Association ________ Association ___ Association The values in both data sets ________ or _________ at the same time. The values in one data set ________ as the values in the other set __________. The values in both data sets show ___ _____________.

#3 Steps for Drawing a Line of Best Fit (cont.): 3.) Draw a line of best fit. It should be as close as possible to most of the points – look for the _________ – and go in the _______ direction as the points. Try to draw the line so that about the _______ number of points are _________ the line as ________ the line. Draw the line so that it goes through some corners where the grid lines meet (integers) to help you write the ___________ of the line of best fit in ______________________________.

#4 Writing an Equation for the Line of Best Fit Once you’ve drawn a line of best fit, you can find the slope, y-intercept, and write the equation of the line – just like with any____________________. Slope: Pick ___ points on the line where it meets the corners where the x & y grid lines intersect (to get integers). Then use the . Y-intercept: Use _______ and ___ point (x,y) in the slope-intercept form (y=mx+b) and solve for b. Equation: Write in slope-intercept form: __________ using the m and b values you calculated.