1. Max’s 2 – year checkup

2. Weight 8o th percentile (also written as P 80 ) Length 90 th percentile (or P 90 ) Head Girth 85 th percentile (or P 85 ) What does that even mean, Dad?

3. Weights of 100 randomly selected 2 year old white American males (in pounds) 243129 252728272625 26293126293029 2028 20212731302829333129 27282928312831272931 29252730293027242928 26 3031293029 2330 31293022242527302624 252928312522272826 273129202328252224 25312431 252728 29

4. Weights of 100 randomly selected 2 year old white American males (in pounds)

5. Tell me everything you can about the weights of these 2 – year olds...

6. So...what’s with Max’s “80 th Percentile”?

7. How many of these 2 – year olds weigh less than 26 pounds?

8. How many of these 2 – year olds weigh less than 29 pounds?

9. How many of these 2 – year olds weigh less than 31 pounds?

10. So, Max is in the 80 th percentile for his weight, because, at 31 pounds, he weighs more than 80% of 2 – year old boys. In general, a percentile (or percentile rank) is the proportion of data that a given point exceeds. However...

11. It might be easier to see the percentiles with the a cumulative frequency histogram...

12. ...or an ogive.

13. An ogive you might see one day (or maybe already have!)