Unit 2, Inventing Center, challenges students to create a method, a series of steps that anyone could follow, to estimate the "true"or real measure of the length. The displays generated during the previous unit guide students’ invented methods. Students compare their methods with those of others, focusing on what aspects of the data the inventor employed to generate the measure. The big idea is that a statistic—the result of applying the steps of the invented method—measures a characteristic of a distribution. Here that characteristic is the central tendency of the collection of measurements. Students compare their methods with traditional measures of center: mean, median, and mode. Typically, students’ inventions include the median and the mode. Further investigations in the unit explore properties of the mean as a fair share and the median as the point that splits the data into two equal-number shares (50%). A teacher supplement describes an investigation of the mean as a balance point. Progress in student conceptions of statistics is illustrated by the Conceptions of Statistics construct.