Monday, May 18, 2015

Ketchup (Guess vs. Estimate)

I had breakfast at a restaurant this weekend and noticed the ketchup bottle on the table. You know, the bottles that are red plastic? That are supposed to appear full? I always get a kick out of these bottles. Here's why..
I immediately wonder how much ketchup is in the bottle?

Take a second to think how almost any answer is pure GUESS.

WHAT information would you want to know here to make an estimate and not a guess?
HOW would you go about getting the information to make an estimate and not a guess?

The second I do this...
I know WAY more information. It's no longer a guess.

Think of other senses that could be used to make a better estimate. 
*One scenario would be something along the lines of me watching the customer(s) before me to see how they held the bottle. How did they shake the bottle? How many people at the table used ketchup and how much?
But that's just plain weird...

Sure, pick up the bottle. Formulate an answer and be ready to back it up with a reason. Don't skip this reasoning part. The bill depends on it!

Let's now move to the answer. Let's say we have more information now.
How would you describe your answer?
How might someone else describe their answer?

Could we say any of the following?
  • It's half full.
  • It's about 3 squirts.
  • It's two-thirds empty.
  • It's about a pound.
  • I could eat 5 french fries with that.
  • It's about 8 ounces.
  • [insert other]
Here's where specificity matters. How should we agree to quantify the amount of ketchup in the bottle? Should we agree at all?

This ketchup bottle context is one of the simplest contexts I've come across in awhile. Here's why:
  • The question is straightforward.
  • You demand more information to do anything better than a pure guess.
  • With one small piece of information, your guess should now be an estimate!
In case you're wondering about the time of day, I don't think it really matters here. The bottle was about a quarter full and this was at breakfast time. It's not like someone went around the night before and filled every ketchup bottle. Which begs the question: 
Is it more efficient for an employee to go around lifting all of the ketchup bottles to determine if it needs refilling or should they just wait until a customer says, "The ketchup bottle is empty, can we get a new one?"
Why haven't you seen more Estimation 180 challenges that deal with weight, density, etc? They're tricky to capture. I wish I could fix that, but I digress. I'll put that onus on you. 

My charge to you is:
No matter what grade level you teach, bring in an item like the ketchup bottle. Ask a simple question where the answer is pure guess and students demand more information to make an estimate. Literally, keep track of all the questions/demands students formulate. Report back.
Classroom (or lesson design) application:
  • Design lessons with less. (notice "less" is in "lessons")
  • Ask straightforward questions that demand more information.
  • Use information to move away from guesses and into estimates.
  • Is it more effecient to go around asking our students what they're stuck on and re-filling them with information or should we wait until they realize their stuck and we help them get unstuck?
Lots for me to think about. Feel free to chime in with some advice. Thanks.


P.S. This reminds me of one of my favorite jokes:
A momma tomato and baby tomato are walking down the street. The baby tomato falls behind because it's going slower. The momma tomato turns around and stomps on the baby tomato, yelling "Catch-up!"


  1. I love the simplicity of this context and as I sit here, I want to pick up that bottle of Ketchup. I shared your post with my wife (1st grade teacher) and she mentioned using a wrapped present with her students earlier this year.
    The unanimous question: what's in the box?
    They weighed it and measured it. Estimations were made before and after touching the box. They also discussed the type of wrapping paper to identify the gender. She gave them a week to come back with a guess based on the information they discovered. This context is not as quantifiable as the Ketchup bottle but the question and requirement of needing to know more information was spot on.
    Now you have me looking for more....thanks a lot!

    1. Do I sense some sarcasm with that last "thanks a lot"?
      I'm glad to get you thinking and I absolutely love the "what's in the box?" activity your wife shared. That's awesome... I love the idea.