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September 11, 2005


Moebius Stripper

Oooh, I'm going to have to blog about something related to this. I know that ignorant people's ignorance often accounted for their ignorance about their ignorance, but I'm still amused that the line of best fit for perceived ability is practically horizontal. Wow.

Regarding giving marks for "I don't know" - I've done something similar. If a student answers a question incorrectly, and can identify that their answer is wrong, and explain how they know that it's wrong, I'll give at least half credit (sometimes as much full credit minus one mark). So, an answer of the form, "Hmm, the price of a widget that maximizes profit can't possibly be $5, because then the profit is $100, whereas a price of $4 gives a profit of $120" will get a fair bit of credit.

I think that four students have taken advantage of this in my entire teaching career.


I like the "This must be wrong" idea!

Students take full advantage of my "I don't know" rule, at least once they realize that I'm serious. I've actually had a student take an algorithms final exam in two minutes—just enough time to write his name and "I don't know" seven times. He still failed, but it was close.

It occasionally backfires, though. The last time I taught an undergrad class, a few of them criticized the policy because "it discourages us from even trying". (I told them they were missing the point.) Several times that semester, students asked me during an exam "Is this answer worth more than 'I don't know'?" (I told them I didn't know.)

Moebius Stripper

Yeah, I can imagine that students would probe for loopholes to the "I don't know" rule. And I don't like to discourage students from trying - what I want to discourage is students not thinking about what they're doing.

Also, the following has not been my experience - The hardest thing for many people to learn, especially in a subject that they've never seriously encountered before, is that they don't know what's going on, that their opinions are not facts, that their intuition is not proof. No, I had a lot of precalc students last year who were well aware that they didn't know anything - they freely admitted that they were never good at math, that they just weren't math people, that they didn't "get" [fractions | graphs | word problems | numbers], what have you. The problem is that many of those same students were highly indignant when their marks reflected that - they're trying, therefore, don't they deserve A's? It wasn't that they didn't realize how little they knew. It was that they thought that their grade should be correlated more strongly with the grade they wanted, than with their level of understanding.

(Aside - I am tutoring a grade 12 student, who, two months ago, couldn't do early elementary school-level math. No joke: he couldn't add single digit numbers without a calculator. So, forget any level of algebra. I've been meeting with him 6-8 h/week, and he's now halfway though his class. His mark? An A-minus. To his credit, he's working really hard - but this kid is not doing A-minus-level grade 12 math. Suddenly, the "I am no good at math / give me an A" complaint makes a lot more sense, in a nonsense sort of way.)

Shripad Thite

Apart from the excellent discussion, I really enjoyed the Lake Wobegon reference. I miss NPR ... but then again WILL does stream online.

(Mitch, are you reading this? If you had paid membership dues to WILL, you would have felt less guilty listening to them in Germany.) :-))


i agree with möbius...the flat graph of perceived ability is fascinating. i mean, i think i'd know if i had done well on a test on logic, for example, and i'd probably rate my ability on that one pretty high. same for grammar due to, i don't know, my degree in linguistics. not sure what i'd do about humor, although i'm not sure how you can take a test about that.

but i've also said that you get more points on my tests for a wrong answer if you tell me why you know it's wrong. as in, "the area of that lune can't possibly be 6 minus 3 pi."

i also try to be as forthright as i can as diplomatically as i can when a student just doesn't get it. but that gets me into trouble with parents sometimes. my best technique: when a kid doesn't get something recognizably simple in a conversation with me i let them struggle with it for a long time until they just have to admit they don't know the answer.


What I find most interesting on the graph is how accurately realistic the B-students are! The 3rd quartile X 60 percentile folks just nailed it - the match between perceived ability and real ability is uncanny!

Anonymous, Please

"One reason is that people seldom receive negative feedback about their skills and abilities from others in everyday life."

I wonder if the Mayor of New Orleans and the Governor of Louisiana know how badly they have bungled *their* jobs with respect to Katrina? When events happened mostly as predicted in advance, they immediately began blaming the federal government for the problems, and everyone else seems to have joined in. Maybe some should spread a bit more honest feedback their ways.


Wheres the pancakes?

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