Homework #1

I was reminded of this homework problem that I give my students as I was riding in on the F train this morning. It is a very good problem because it is exceedingly simple and nicely demonstrates two problems of the classical way of looking at statistics.

All you need to do this homework is a busy place and some free time, about 20 minutes.

Find a spot where people congregate or pass by. Be sure to carefully and concretely specify this place: keep its boundaries fixed and rigid for the duration of the homework.

Count the people in the spot, either all at once, or as they pass by for some fixed time (decided in advance). Also count the number of people who are wearing some sort of thinking-suppression device. There are obviously any number of other things you can take note of, like sex, age, etc., but we’ll ignore all of them.

Report back to me (in the Comments) the two numbers, number wearing thinking-suppression devices, which will be less than or equal to the total number of people. Also note details of your spot.

We are obviously going to be talking about forming ratios and estimating probabilities. I’ll discuss what all this means–and what it does not mean—once a few people have turned in the assignment.

Oh, yes. A thinking-suppression device is anything like an I-Pod, MP3 player, etc. etc.


  1. Bernie

    How do I categorize a cell phone? Is it a thinking-suppression device or a thought projection device or both? I ask because since it can be unclear whether an earpiece is for a music player or cell-phone or both? Does this question matter for the assignment?

  2. Larry Sheldon

    Teacher riding the “F” train.


    I would have said that thought is orthogonal to the devices named, and their kith.

  3. Briggs


    Excellent question.


    You wouldn’t say that if you would have seen my last class.


  4. Demesure

    I have a live webcam in Lahsa/Tibet, and I count a lot of machine guns
    Is a machine gun a thinking-suppression device ?

  5. Steve Hempell

    Homework Assignment

    Live in a small town so “busy” is hard to find.

    Time 30 minutes from 14:58 to 15:28, Population of town ~2300, 12 Deg C, Sunny with cloudy periods. Spring Break ie no teenagers milling around after school.

    People passing by 41 (counted only once)

    People with thinking-suppression device 1

    Area surveyed – Sat on bench on main street. People had to pass by me from one side to the other behind me, across the street or walk in the crosswalk just to one side of me.

    Probably not a good sample size, but it did my homework and the dog didn’t eat it!

  6. Tim James

    Here’s my homework:

    Total sample size: 373
    Those wearing TSDs: 30

    Position: Camden High St. exit of Camden Town Underground. Time: 12:03 – 12:23 Date: 18/3/08

    It’s been a long time since I handed in homework. Are stars still awarded?

  7. Briggs

    Tim & Steve, you both get two gold stars. And one red one. I hoping for a few more answers before I post the answer.

  8. 2008-03-18 11:46 CET, inside the rear section of light rail from $SMALL_TOWN to $LARGER_TOWN, in between two stops.

    6 persons (including myself), 1 actively using a cellphone. I cannot tell whether the cellphone worked as a thinking-suppression device as she was speaking Russian.

    One stop and one minute earlier it would have been 4/0, should that matter.

  9. Steve Hempell

    Addendum to homework assignment:

    One other person was wearing a thinking-suppression device but was not “plugged in”. My criteria was that the device had to be plugged into their ears. Actually they plugged it in when they passed on the other side of the road, but that didn’t count either.

  10. Bernie

    Quit grinning. Don’t go professorial on me. What is the answer to the question.

  11. W J B

    Coffee Shop patio near office. Roughly 20 minutes. I’m gonna say about 25 outside tables equipped with three seats each litter the area. Only counted MP3 players and video games–phones aren’t TSD right?

    26: 103

    *In Shanghai a lot of girls read books/articles on there Nintendo DS’. No way of knowing the thoughts supressed or created.

  12. Would that include the Blackberry I am using to read this right now?

  13. GeorgeM

    While my wife shopped in one store in the mall, I sat on a bench out front and counted 105 people passing by in front of me. 100 were unencumbered, 3 women and 2 men were actively conversing on cell phones. Elapsed time, about 15 minutes.

    Amazingly, I saw not one IPOD or other device with earphones or whatever thay are called during the entire time we were in the mall.

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