If you asked me to name something that’d trigger a teenager’s passion, I wouldn’t leap at “Correctly Guessing a Has-Been Celebrity’s Age” straight away. But there they were, hollering, competing, and rallying over near misses like frat boys over fantasy football.

- You have your students make three columns: Name, Guess, and Actual.
- You project twenty-or-so celebrities (a broad range of ages) onto the wall. You have ’em guess the age out loud.
- As they toss out guesses you say, “It’s probably a
*bad*idea to toss out your guess. We’re all competing for the title of Best Age Guesser. Keep ’em close.” - You keep projecting, they keep guessing. Maybe you ask ’em, “twenties or thirties or forties?” to keep ’em participating together.
- Then you go
*back*through and give the ages. They write those under the “Actual” column. Watch ’em get crazy here, freaking out ’cause they were only three years off Natalie Portman’s age. Watch some of ’em blow Nelson Mandela by*decades*.

**Enter the mathematics here:**

- You ask, “how do we decide who guessed the best?” Expect intial suggestions like, “Whoever guessed the most right.” and “Whoever got closest to each age.”
- Take care of that first suggestion by asking who got the most right (Vicki, let’s say) and then ask the class, “Can we stop searching for the best guesser now? Is Vicki guaranteed? Why not?”
- Ask for clarification on the second suggestion. Get to a place where they’re subtracting the actual answer from the guess, getting negative numbers for underguesses and positive number for overguesses.

Make the math as hard or as easy as you want here.

**Algebra and Below:**

- Someone will suggest you add the new column of numbers up. You ask, “What number do we want there?”
- Someone’ll suggest “Zero.” You talk about the girl who overguesses Tiger Woods by 30 years and
*under*guesses Oprah by 30 years.Girl has a zero but couldn’t guess your age if you handed her your driver’s license.

- “So what do we do?”
- Drop the negatives. It doesn’t matter if you guess over or under, only that you’re off.
- Have them find the mean of their new column, full of positives. What does it mean? (The average number of years they were off per guess.)
- Ask if it means they guessed over or under on average. (Can’t tell, we dropped the negatives.)
- Have them find the average
*including*the negatives. (“Who guessed under on average? Who guessed over?”)

**Algebra II:**

- Connect this to absolute value.

**Calculus:**

- Talk about why the square of the differences is preferable to their absolute values. (x
^{2}is differentiable where absolute value isn’t.)

Give the winner a fun-sized candy bar. Let her select a celebrity for inclusion in next year’s lineup.

**Attachments:**

- Keynote
- PowerPoint
- PDF (Obviously you’ll need to update the ages here.)

**Credit Where It’s Due:**

Got this idea from my ed-school mentor several years back. Yo, AB, I still use your stuff, man.

[**Update:** Matt has some pretty priceless extensions to this lab.]

How does the Mean and Median of all student guess do in this competition?

Creating a histogram of the guesses.

Looking at the standard deviation of the student guess. Do standard deviations vary with the age of the person.

And I reply:

Oh yeah, thatâ€™s great. Itâ€™s so clear now. I need to feature as many or more celebrities as there are students in the class. After the main event then I assign a celebrity to each student, they collect the guesses from around the class and perform a statistical analysis. Maybe I have Keynote slides set up so they punch in their data and present it real quick.

**For Your Consideration:**

Peace and prosperity. Vote **dy/dan** best new edublog and best individual edublog.

## 18 Comments

## ken

November 27, 2007 - 11:24 am -ya know? I shared this with algebra teachers today. They were quite ‘ho-hum’ about the whole thing.

but it’s not about the lesson you present here; it’s the ‘hey-I-didn’t-create-it-and-I-didn’t-find-it-on-my-own-so-thank-you-but leave-me-alone’

Now playing: sadness.

## Sue

November 27, 2007 - 4:05 pm -Awesome idea…although I do not teach math, I’m thinking the underlying foundation of the lesson (celebs, guesses, then learning integration) can work for any classes. Thanks for sharing!

## Graham Wegner

November 27, 2007 - 4:29 pm -Dan, you saved my day. Just when I needed some more insight into my class’s initial algebraic reasoning, your post pops in my aggregator. I’ve modified the ppt to include some Aussie celebs and altered the DOB data for an Aussie classroom – do you mind if I share the downunder version via my box.net? Let’s see how this goes with 11/12 year olds – I like the fact it is modifiable for whatever age group. Cheers!

## dan

November 27, 2007 - 5:30 pm -Ken: Bummer. However it’s true that, as far as deep mathematical analysis goes, the activity’s kinda weak. Really awesome for the day before [whatever] break when you’d rather not cop out with a totally irrelevant [whatever-themed] movie, though.Sue: I’d love to read about any translations you come up if you felt like posting them to your blog.Graham: Do it, man, and send me a trackback so I can check it out and introduce myself to your Australian celebrities. You’re right on that this activity scales nicely to a bunch of ages.## Matt

November 28, 2007 - 8:21 pm -Great ideas. A couple other things that you might try:

How does the Mean and Median of all student guess do in this competition?

Creating a histogram of the guesses.

Looking at the standard deviation of the student guess. Do standard deviations vary with the age of the person?

Again great idea. It is so important to introduce mathematical topics with a context that the students can really connect to.

## dan

November 28, 2007 - 11:11 pm -Oh yeah, that’s great. It’s so clear now. I need to feature as many or more celebrities as there are students in the class. After the main event then I assign a celebrity to each student, they collect the guesses from around the class and perform a statistical analysis. Maybe I have Keynote slides set up so they punch in their data and present it real quick.

Thanks, man. Great extensions.

## J.D. Williams

December 1, 2007 - 8:33 am -I think you should make one of these a week.. haha.

I used it on Friday and my students really liked it. A lot of my students thought that Nelson Mandela was Bill Cosby, so I don’t know if that says more about their knowledge of world leaders, or how they think Cosby would look in a current picture. I had more fun watching them trying to guess the names than most of them did with the whole activity.

You don’t even have to give out candy bars to get them interested. I gave out a couple of folders, a keychain flashlight I had gotten at some district function, and a small notepad with monkeys on it (I have no idea how that got into my supply closet, but it was the “prize” most of them wanted).

## Erin Remple

December 11, 2007 - 11:44 am -This is so fantastic! I’m a math teacher and feel rather uncreative most days. However, if I’m given a starting point I can often develop new ways to use it. Thanks for giving me an exciting starting point (which I’ll use for teaching standard deviation in Consumer, and line of best fit in pre-cal)!. What other interesting things do you have lurking in your database of ideas?

## dan

December 11, 2007 - 3:29 pm -Glad to see you’re enjoying things around here, Erin. I do have this one lesson which takes a student from year-one algebra through calculus in one fun-filled, engaging afternoon. Just haven’t found the time to post it for some reason.

## Elissa

September 15, 2009 - 8:48 pm -I can’t get it to open. When I extract the file, it opens up PowerPoint but there’s nothing there. Hmm…must be my computer.

## Sue

September 16, 2009 - 7:50 am -I get a 4.5 meg file, and it looks great at first, but after Colin Powell the photos are missing. (My computer is using NeoOffice instead of Powerpoint. If the photos are in different formats, maybe that’s causing the trouble?)

## Dan Meyer

September 16, 2009 - 4:30 pm -I can’t troubleshoot Microsoft. Here’s a PDF, though. Or you can also grab celebrity images of your choosing from Google Images yourself.