MTH 232
Section 13.2
Measuring the Center and Variation
of Data
Overview
• The center of a data set can be defined in
three ways:
1. Mean
2. Median
3. Mode
Mean
• Also referred to as the arithmetic mean, or
average.
• Add up the data values, then divide by the
number of data values.
• Can be modeled using manipulatives.
• May or may not be the “best” center,
depending on the number and quality of
outliers.
Median
• The “middle” of the data when the values are
arranged from smallest to largest.
• The number of data values to the left of the
median will be equal to the number of data
values to the right of the median.
• Be sure to reference the “other” definition of
median as a way to help students remember.
• Lining up students from shortest to tallest is a
good activity to demonstrate median (be careful
to use an odd number of students).
• Median is unaffected by outliers.
Mode
• The data value (or values) that appears (or
appear) the most.
• It is possible for a data set to have more than
one mode.
• It is also possible for a data set to not have a
mode.
• Mode is unaffected by outliers.
Let’s “Describe” our Class!
• What “value” do we want to use?
• For the chosen measure, find the mean,
median and mode.
• Which measure of central tendency best
describes us?
• Add to homework set: 17, 18, 19