Center and spread – kicking a ball in the schoolyard

MathematicsStatisticsAges 15–16

Four screens use ball kicks in the schoolyard to explore the mean, the median and measures of spread of a data set. Median screen: balls are kicked along a distance axis and students predict the median with an arrow before seeing the correct answer. Mean & Median screen: the kicks sit on a seesaw; drag the fulcrum to find the mean and compare it with the fixed median marker, seeing that the mean changes continuously while the median only jumps in steps. Spread screen: compare two groups of kickers using the range, the interquartile range (box plot), the variance and the standard deviation. Lab screen: add or remove kicks one at a time and watch every statistic update instantly. Based on the "Center and Variability" simulation by PhET Interactive Simulations, University of Colorado Boulder (CC BY 4.0); rewritten.

Lesson: Mean, median and mode