2 meetings ago, I went in to develop a lesson on mean and median. I mentioned how I always struggle with students realizing how an outlier can effect mean much more than median. Through discussion and brainstorming we came up with a great idea using blocks, a meter stick, and a balance point. This lesson would have never come together the way it did without my PLC group.
The lesson involved creating sets of data with a mean of 50. A meter stick was then balanced and blocks were placed at the data points to create a balance. Students were asked to put on an "outlier" block and recalculate the mean and median.
This activity was also used to visualize missing data point problems with a given mean. Students placed blocks on the meter stick and saw how it didn't balance. Then they were asked to place a block so the meter stick would balance at 50 (have a mean of 50).
A quick bare-bones handout can be found here.