I do this activity with my freshman pre-algebra class to have them get experience with graphing "real data" points, then finding the slope of the "best fit line" and making meaning of what they did. A regular question in math class is "when am I ever going to use this?" This activity gives them something tactile to do with their hands that then makes the data points and the graph itself have real meaning for them and not just be numbers / dots on the page. I follow this activity up with "Graphin