How Do You Find the Line of Best Fit?

To find the line of best fit, create a scatter plot using the available data, then use a pipe cleaner to find the position of a line that is as close to as many of the points as possible. Choose two points along this line to find the equation.

1. Estimate the direction of the line of best fit

Graph the points of the data. Set a pipe cleaner or piece of dry spaghetti in a position that appears to be as close as possible to as many of the points. Mark points on the graph paper at the beginning and end of the pipe cleaner or piece of spaghetti.

2. Find the equation of the estimated line

Write the coordinates of the two endpoints as (x1, y1) and (x2, y2). Find the slope of the line by plugging the coordinates into this formula: slope (m) = (y2-y1)/(x2-x1). Write the equation using point-slope format (y-y1 = m(x-x1)).

3. Predict further points in the line of best fit

Plug additional x values into the formula to find y values on either end of your estimated line of best fit. Refine your line as needed if values further down your estimated line deviate visibly from the plotted data.

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