Lesson 4: Appropriate Measures6.DS.6d

I can…

I can choose the best measure of center for a data set based on its shape.

Key words

• Mean — The average. Add all the numbers, then divide by how many there are.
• Median — The middle number when you put them in order.
• Outlier — A number that is much bigger or smaller than the rest.
• Skewed — When most data sits on one side with a tail on the other.
• Data distribution — How the data looks: where it sits and how spread out it is.
• Variability — How spread out the numbers are.

Steps

1. My data, the top scorer's points: 22, 24, 20, 25, 23, 21, 58. I notice 58 is much bigger than the rest, so it is an outlier.
2. Mean: 22 + 24 + 20 + 25 + 23 + 21 + 58 = 193, then 193 ÷ 7 ≈ 27.6.
3. Median: in order they are 20, 21, 22, 23, 24, 25, 58. The middle (4th) value is 23.
4. The mean (27.6) is higher than 6 of the 7 games because 58 pulled it up. So the median (23) better shows a typical game.

Try it

Data set: 15, 18, 16, 17, 15, 72. Which measure of center best represents the data?

Check your answer

Median, because 72 is an outlier

The value 72 is an outlier. The mean (25.5) is pulled high by 72 and doesn't represent the typical values. The median (16.5) is a better measure of center.

Sentence starter

I know ___ because ___.

Goal: I can explain my choice using the words mean, median, outlier, and skewed.