So Happy Together #1

I’m compiling notes for a presentation entitled Getting The Most Out Of Your Digital Projector (I know. Really catchy.) the main thrust of which is that my instruction has never been happier than when I made friends with:

  • A digital projector, and
  • A laptop.

One reason why:

The story goes that during World War II, Allied pilots were taking a beating. There was a very limited supply of retrofitting armor at the time so the Allies hired a statistician to determine where and how they might best allocate it.

The statistician took a top- and right-view diagram of the planes out to a runaway and watched the planes land. He marked a dot wherever he saw bullet holes and came back with something like the slide below. [cf. Abraham Wald’s original study.]

So after you tell your class that story and after you show that slide, you ask the question, “Where would you put the armor?”

You insert the question real quick and you turn your inflection up at the end like it’s just a quick set-up for the real question when in fact, nah, this is the only question.

They walk right into it and tell you they’d attach the armor where all those dots are clustered.

Then you tell ’em, “Nah, see, mister statistician put the armor where you don’t see dots.”

And I tell you: there isn’t any correlation between the age of the student and how long it takes her to figure out why.

See, I first told that story last year. I happened upon it ’cause some friend linked to some other blogger who linked to it out of someone’s feed.

Basically there was no way I’d ever find it again this year. I mean, maybe I’d remember the story but odds are slim I’d relocate that image again if not for the fact that my lightweight presentation files (a few megabytes per week) let me save every fun thing I’ve ever shared with my class. Forever.

And now this year, the same friend links to kottke who links to waxy via boing boing who gives up some other cool thing to share with my class. And suddenly I’ve got two awesome thought-provocations to spread over two days.

How long until I have 180 provocations for every day of the school year? No way to tell but given how happily my laptop and digital projector play together, I can only surmise: not very.

[Updated: to add a citation link to the source (courtesy Tim) and to clarify for anyone who thought I was claiming authorship for this anecdote or the illustration, I wasn’t. This post was explicitly about effective storage of found online resources.]

[Updated again: to add a link to Abraham Wald’s original study.]

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I'm Dan and this is my blog. I'm a former high school math teacher and current head of teaching at Desmos. He / him. More here.


  1. Because I love titles:

    1. PRO-jection
    2. For your display…
    3. The allegory of the projector
    4. You and your projector – perfect together
    5. Hoisted power
    6. Visualization meets internalization
    7. Me project pretty one day
    8. The proverbial light bulb is real!
    9. A lucent lesson
    10. Brite-Lite: new and improved
    11. Watts the frequency, Kenneth?
    12. Ohm my! Is that a projector I see?
    13. Go candle-less!
    14. Pho’tons of fun…use a projector!
    15. If you love tungsten filament…
    16. When light hits a lesson
    17. GE: Bringing good lessons to life
    18. Getting the most out of your digital projector

    something oddly familiar about #18

  2. I like the story. And I got it, fast. Makes sense, right?

    But I missed something. What does this have to do with a projector? Couldn’t you hand it out?

  3. Yeah, I buried the lede deep beneath that anecdote.

    I probably coulda saved that anecdote in a three-ring binder somewhere. Or maybe I could’ve kept a running file on my computer with fun digressions.

    But in terms of preserving the image, the anecdote, the original URL, and the formatting of the picture, nothing’s worked for me as well as setting up a Keynote presentation file for each week of the year and then backing up constantly.

  4. Damn it. I’m an idiot. Explain it to me. And what does the Wired story have to do with any of this? Sometimes I hate you, Dan.

    P.S. Why is this image of the plane also in your Tiger Woods entry?

  5. The Wired story is entirely irrelevant to World War II and only a little more relevant to my use of a projector + laptop to store cool stuff.

    That image of the plane showed up with Tiger Woods ’cause I overwrote a file. And since you did me a solid right there:

    Some Allied planes didn’t make it back to the runway. They were shot down. (Obviously, right?) Planes that got shot along those dot clusters, well, they were see-through but at least they came back.

    So you’ve gotta ask yourself: the planes that were shot down, where did they get hit?

  6. I was explicit that I found the story and link “’cause some friend linked to some other blogger who linked to it out of someone’s feed.” I ran several searches through Google before posting but couldn’t find a citation.

    If this weren’t such a willful misreading of my post, I’d be grateful you found the link for me. I’ve amended the post in any case.

  7. Personally, I love when a reactive tangent distracts from the point of the conversation…and lesson. Human nature is such an intriguing concept, especially in the high intensity drive-by world of blog commenting.

    Great anecdote, Dan. Like my own utter fascination with the Mann Gulch wild fire ‘leadership’ question/story that I’ve used in countless public presentations, the fighter plane model is ripe for the picking…and something tells me that nobody thinks I actually made up that story (or claimed to have done so). Why they think you were claiming credit is a bit…curious. Yes, a more stringent ‘citation’ mention (or clearer anecdotal path as to why it didn’t yet exist in your possession would have helped)…but the comments above are distractions of the real point at the end of the day.

    Keep on keepin’ on, my friend. 356 days of provocations…or at least 180, huh?! NO rest for the innovative and weary.

  8. I bet any biologist readers got that one faster than the rest. I figured it out, but not quickly, and probably in spite of Physics training rather than because of it.

  9. I know this is an old thread now but wanted to note that the name of the original study is “A method of estimating plane vulnerability based on damage of survivors” by Abraham Wald which can be found in google scholar.