> Now call out to the students who are sitting near where you hid the envelope: “Um, uh, what’s that over there . . . is it an envelope??? Really? What’s inside? Could you open it up?” A student opens it and reads out what’s written on the sheet inside: “Your guesses are all too high!”<p>Maybe it's because I recently did some reading about magicians, but if I were one of the students I would be thinking that he could have any number of hidden envelopes with different predictions, and he just chose the one that ended up being correct. Of course, I'm deliberately missing the point of the story.
The "wisdom of crowds" part of the title is a bit unfortunate. While there can be systemic problems with that type of approach, this does not really demonstrate them.<p>What is demonstrated is when you give the students an algorithm for a biased estimator, the estimate they get is biased. This is good; empirical demonstration is useful... but it isn't the wisdom/unwisdom of crowds, really.<p>edit: good responses! Unfortunately I don't have enough time right now to properly clarify how/why I'm looking at it this way.
In this day and age nobody is going to hand the scale to the next group with the bag sitting on top of it? Its a bit cynical but I would expect that some pairs estimate to be really really close if not spot on as an effect of they just weighed the bag directly.
People forget that Galton's original example was with a group of people with good domain knowledge. It would be interesting to try the experiment on a group of old-school sweet sellers.
I wonder if he just asked the students how much the bag weighed without giving a scale if you'd get a better answer.<p><a href="http://phenomena.nationalgeographic.com/2013/01/31/the-real-wisdom-of-the-crowds/" rel="nofollow">http://phenomena.nationalgeographic.com/2013/01/31/the-real-...</a><p>This post is more "ask a bad question, get a bad answer".
When you shake the bag, smaller candies settle down to the bottom, the larger ones get to the top. So even if someone tries to shake the bag to get a 'random' sample, they will be getting a biased sample if they pick all 5 candies from the same layer (usually the top).
A wonderful demonstration of statistics.<p>On similar ground, this reminds me of Deming's red bead demonstration, relating statistics to corporations and management practices. Best explained dynamically: <a href="https://www.youtube.com/watch?v=JeWTD-0BRS4" rel="nofollow">https://www.youtube.com/watch?v=JeWTD-0BRS4</a> (delightfully, this is posted by the Mayo Clinic).
Kind of surprised that kids don't realize this.... What grade is it in?<p>The first reaction I think any class I was in would have to this demonstration would be to figure out how we're being cheated.<p>Given a bag with a random sampling of candy and being told to 'pick 5 pieces' I doubt I would choose 5 of the same large candy bars.<p>It seems highly surprising that 100% of the time this is done you don't have a single pair of students reaching just a bit further into that bag.<p>It doesn't even seem to be a particularly impressive demonstration.
I would really have expected atleast a small number of people to have carefully looked to workout the distribution and whether there were a higher density of one type (e.g. small) at one position.<p>I imagine the use of a bag rather than a Jar as per the usual school fair game could make spotting these harder though (unless they're allowed to pick up the bag).