Friday, July 18, 2008

Off The Charts


Maddie had her 24 month checkup this week. She's all good and healthy and cute. Inevitably in these check ups, the CDC height and weight chart is brought out to track the child's growth compared to the rest of the population. We were wondering where Mads would fall in the height chart because we know she's very tall.

We have to get some basic statistics straight first. There is only one data point at the top. The 100th percentile is represented by the tallest person in the population used for the study at that age. Everyone else is shorter than that person. You cannot be "off the charts" or over 100th percentile. If you were taller than the 100th percentile person, you would be the new 100th percentile person and the scale would need to be readjusted.

Having said that, Maddie is "off the charts" in the common vernacular. She is 24 months old and 37 1/4 inches tall, which puts her well above the 97th percentile, which is the highest curve shown on the CDC height charts.

When you get that far out towards the tail of the bell curve, there are fewer data points and it's more difficult to trust the curve. That's why they don't draw a 100th percentile curve - it consists of only one sample at each age and would be highly variable. Our daughter is probably 99th percentile-ish.

No matter though. Chart or no chart, Maddie is one super-tall girl. She towers above her peers. Let me put this another way to illustrate my point in a way no chart ever could:

She is average height (50th percentile) for a THREE YEAR OLD and she is only TWO!

2 comments:

wildmary said...

Tall girls rule, Maddie!!

ingrid said...

Yikes! Where does that put Madeline who was 37 3/4" at 2? Although the measuring system our ped uses is hardly scientific.