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Parody Critiques Popular Khan Academy Videos

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Re: Parody Critiques Popular Khan Academy Videos

#21

Post by hdevalence »

sanderjd wrote: post #17

What is a good non-rules-based approach to teaching why a negative times a negative is a positive? I've seen a proof-through-absurdity showing that if -1 * -1 = -1, then you can make 0 = 2, and a proof using all three negativity permutations, and setting two different distributions equal, showing that ab = (-a)(-b), but the math for both of those approaches seems to be more advanced than the rule.

Say that multiplication by -1 is a 180 degree rotation of the number line. Then -1 * -1 is a 360 degree rotation -- which is the same as a 0 degree rotation.

Note that saying it like this is non-intuitive, but the point is that it's actually a geometric interpretation, so you draw a picture. This also helps students with the idea that there's actually some connection between algebra and geometry --- even though this is really fundamental, it's often omitted from mathematics education.

Re: Parody Critiques Popular Khan Academy Videos

#22

Post by p2e »

schiffern wrote: post #12

FTA: >Salman Khan, uses positive and negative signs inconsistently and mixes up transitive and associative properties. Oh, the irony: Khan actually confused the commutative and transitive properties. The parody video gets it right: http://www.youtube.com/watch?v=hC0MV843_Ng#t=3m14s This stuff is hard. To be fair, I don't think Khan is doing any worst than a first-year teacher in his first class of the day. Youtube pr…

I think that this is a serious issue. Khan usually just hits record once, publishes, and never revisits his videos again. By his own admission, he takes some initial feedback (first few video comments) from his videos but only applies it to his subsequent lessons not bothering to fix the prior lessons. This allows him to produce a lot of content, but it can end up doing more harm than good by keeping a lot of bad lessons out there.

I've seen quite a few of his videos that have had serious problems in them, 20-second long stretches of silence when he's erasing or fixing mistakes, and places where he talks himself (and the listener) into a circle. I just don't see why Khan doesn't take the time to fix obvious mistakes/issues in his videos -- or have someone else do it! Sure, it means more video development time but it's for the purpose of producing superior lessons and not spreading misinformation.

Traditional educators revisit topics/lessons and learn from their previous attempts and from student feedback. This allows future lessons on the same topic to be more refined and better serve the student. Who honestly believes they get something right the first time, or doesn't try to improve something when they, or someone else, identifies an obvious problem?

Khan has an excellent framework in place, but he needs to revisit his content. Or let someone else do it -- do these videos have less value if someone other than Khan comes in to fix things up? I'm sure there would be plenty of volunteers. Obviously the guys in this video had some good insight that could have helped Khan's video.

Re: Parody Critiques Popular Khan Academy Videos

#24

Post by p2e »

kiba wrote: post #10
tocomment wrote: post #6

Earlier quoted context omitted.

I don't understand. Are you disagreeing? I think leaving the mistake and correcting later is very confusing and possibly discouraging to students. What is your response to that?

I think leaving the mistake and correcting later is very confusing and possibly discouraging to students. What is your response to that? In the same video, note your mistake and correct it.

Why not just re-record the video, or design the videos such that they can be stitched together from small manageable sub-videos that can be easily and quickly re-recorded. There are plenty of times when he "clears the screen" and these would be perfect opportunities to edit together "good" sub-videos in the lesson.

I don't see why you would want to leave the mistakes in there. Someone might not grasp the correction!

Re: Parody Critiques Popular Khan Academy Videos

#25

Post by p2e »

tocomment wrote: post #16
kiba wrote: post #10

Earlier quoted context omitted.

I think leaving the mistake and correcting later is very confusing and possibly discouraging to students. What is your response to that? In the same video, note your mistake and correct it.

That would be better. I think a lot of times he doesn't realize the mistakes until they've been published. And maybe he has a rule he doesn't re-edit videos after they've been published? I just remember getting incredibly frustrated after basically learning the wrong thing in the first video and then having it corrected in the second.

My guess is that he doesn't edit videos after publishing because he likes the youtube stats?

Maybe youtube isn't the best medium for his videos and he should instead find an option that allows and easily facilitates future edits.

Re: Parody Critiques Popular Khan Academy Videos

#26

Post by jmcqk6 »

duopixel wrote: post #8

I do agree with some of the issues presented here. Khan teaches you how to solve many math problems, but he rarely mentions how you could use it in real life . But if you go to the Q&A section you will rarely see this brought up. I do find it appalling that their approach is making a parody video instead of presenting a better solution. Instead of wasting their time—and mine— making fun of Khan, it would have been im…

What you are missing is the long line of criticism that has been made concerning Khan academy for years now from math teachers around the united states, all of which has been basically ignored. You're appalled that a few of them made a parody? How would you feel if you discovered that the only way you could be heard on the topic was by making a parody?

These teachers that criticize Khan, you know what their 'pull request' is? They actually teach in real classrooms. They experiment constantly, looking for better ways to teach, and then they share their ideas with other teachers through a variety of different mediums. Those are their pull requests. You don't see them because you're not a part of the community.

Re: Parody Critiques Popular Khan Academy Videos

#27

Post by JadeNB »

sanderjd wrote: post #17

What is a good non-rules-based approach to teaching why a negative times a negative is a positive? I've seen a proof-through-absurdity showing that if -1 * -1 = -1, then you can make 0 = 2, and a proof using all three negativity permutations, and setting two different distributions equal, showing that ab = (-a)(-b), but the math for both of those approaches seems to be more advanced than the rule.

My favourite motivation is to think of bank accounts. (A less monetary approach would be to think of a rising or falling temperature.) I think that anyone can predict the results of the following four operations:

* make a deposit in your bank account every day, and see your balance in a few days (positive times positive);

* make a deposit in your bank account every day, and see your balance a few days ago (positive times negative);

* make a withdrawal from your bank account every day, and see your balance in a few days (negative times positive);

* make a withdrawal from your bank account every day, and see your balance a few days ago (negative times negative).

Re: Parody Critiques Popular Khan Academy Videos

#28

Post by pflats »

sanderjd wrote: post #17

What is a good non-rules-based approach to teaching why a negative times a negative is a positive? I've seen a proof-through-absurdity showing that if -1 * -1 = -1, then you can make 0 = 2, and a proof using all three negativity permutations, and setting two different distributions equal, showing that ab = (-a)(-b), but the math for both of those approaches seems to be more advanced than the rule.

I've never had to teach this, except remedially, where honestly, time is a major issue. A teacher in my building has students record someone walking backwards down the hallway, then plays the video back in reverse. The student appears to walk forwards down the hallway, more convincingly than you'd expect.[1]

From there, you can show that -(-1) = 1. If the students have any command of factoring, you can use that to handwavingly show, for example, that -2 ✕ -3 = -1 ✕ 2 ✕ -1 ✕ 3 = -(-6)) = 6.

[1]She actually has them walk forwards, and hold signs - it's more involved, and covers all four cases for multiplying negatives and positives, but we'll gloss over that for the moment.

edit: oh yeah, can't use * for multiplication.

Re: Parody Critiques Popular Khan Academy Videos

#29

Post by asto »

sanderjd wrote: post #17

What is a good non-rules-based approach to teaching why a negative times a negative is a positive? I've seen a proof-through-absurdity showing that if -1 * -1 = -1, then you can make 0 = 2, and a proof using all three negativity permutations, and setting two different distributions equal, showing that ab = (-a)(-b), but the math for both of those approaches seems to be more advanced than the rule.

You make your own banking system or something. Say you give a class of 10, $2 each. They all owe it back to you which makes the balance -2 each. So ask them how much you're owed back in entirety. I bet most of the class will crack it themselves without you and your rules :)
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