models · Base rates 15 min · pencil ★★☆

Guess the left-handers

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A base rate is how common something usually is. It helps you make smarter guesses.

Write a quick guess.
Use the base rate to make a better guess.
Ask 30 people (a class, a team or your family and friends). Count the left-handers.

Question: Predict for a class of 30 kids: how many are left-handed?

My quick guess (out of 30):

Base rate: about 1 in 10 people are left-handed. So in 30 kids, about:

I asked 30 people. Left-handed:

Was my first guess or my base-rate guess closer to what I found?

Grown-up corner

Why it matters: People often guess from a story they remember instead of how common things really are. Base rates fix that.

Extend it: Guess how many red cars you will see on a drive, then count.

My brain felt: ☐ easy ☐ just right ☐ stretchy

One thing I learned: ________________________