This is an activity that I use with my 9th grade Algebra 1 students. They are able to pick from US Cities or Car Make and Models, whichever one seems to be more interesting to them. On a separate piece of graph paper, they will create a scatter plot and then answer the questions on the paper. There is a step for them to research and find 5 new cities or cars, which then they will compare to their line of best fit/trend line. It takes about 75 minutes to complete on average.
Differentiation for the lesson could include students graphing the plot on a computer/graphing calculator and actually finding the line of best fit, not just sketching a trend line.