Khan Academy – http://www.khanacademy.org/ – is often cited as a great online resource for learning mathematics and other subjects. I have heard many good things about this website and was wondering in what depth are subjects covered?
I know Khan covers topics in (highschool) algebra and calculus. What other subjects are treated? and at what level? How rigorous is his treatment?
Some background: I teach at a university and would like to know if this is a good resource to point students to. I'm thinking primarily of students who are having trouble in college algebra, calculus I, etc. Not necessarily math majors.
To be crystal clear: I'm not looking for suggestions regarding other online resources. I just want an honest critique of Khan Academy from those who've explored what it has to offer.
Best Answer
I find that the impressiveness of a Khan Academy video for me is negatively related to how much I know of the subject. As a math graduate student and calculus teacher, I find Khan's math/calculus videos the least impressive of the lot, his physics/chemistry/biology videos mildly impressive, and his history videos the most impressive.
What this suggests to me is that the Khan Academy is lacking in depth and clarity of presentation, as well as in addressing the subtleties and key issues that would be necessary to impress a person with some knowledge of the subject. Watching the Khan Academy is roughly akin to having a smart kid in your class (who is learning the subject along with you) explain to you what he/she has understood of the subject. It is not really comparable to how an expert teacher would convey the material.
This may not be completely a minus, because the lack of polish and the chumminess of the videos might itself be an endearing factor that makes people more comfortable with the videos. It also makes it easier to scale up and make a larger quantity of videos. Also, the low intensity of the videos makes it easy for a person to watch them when tired and distracted without missing out on too much.
Here are some examples of sloppiness:
(i) In the calculus videos, when I viewed them, the graphs were drawn very shakily, extremely hard to understand, and not well labeled. (ii) In a video on classical mechanics, there were some inaccurate statements about normal force, describing it as a reaction to gravitational force in the action-reaction sense (this was fixed later, I think). These weren't merely careless errors in speaking, but reflected a deeper lack of understanding. (iii) The examples and symbol choices are often confusing.
If you are recommending watching Khan Academy videos, I suggest you add the caveat that they should not expect a lot more (in terms of accuracy and quality of explanation) than they would expect learning from their colleagues.