What does Khan Academy have to offer? Depth? Rigor? 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. 
 A: I've looked around khanacademy a bit and I'm not really impressed. There's certainly nothing wrong with it, but it gets too much hype. There are math tutors on youtube (look up PatrickJMT) who do a better job.
A: Apart from algebra, some calculus and basic maths the site also covers Geometry and Trigonometry, the 2 subjects that I'm using Khan Academy for at the moment.
The tutorials aren't very rigorous, but that is a positive thing for students who find calculus challenging and are not math majors (that described me by the way).
Although my first ever proof was actually from this site, it dealt with how to prove the angles in a triangle always add up to 180 degrees. It was pretty cool.
I actually think this site really is most ideal for people who need to brush up on their basic math skills before/while taking a first course in calculus.
I also get bored with my head stuck in a book all the time, and it's nice to watch a video once in a while. And finally, the many online exercises keep me from nodding off, and if you are somewhat immature you can take pleasure in collecting badges and energy points, as I do! ;)
A: I've used Khan Academy videos from time to time, and my biggest complaint would be the lack of professional oversight. For example, in his video about the sodium-potassium pump he is just wrong about how the membrane potential is generated, and how the action potential is transmitted. In this case, there is a correction video posted, but I remember there were some other videos with smaller mistakes that were only pointed out in the comments, or not at all.
That said, I still think it's an excellent learning resource, because the short videos are easier to watch than reading the same content in a book, and Khan is very good at explaining things.
A: 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.
A: I use Khan Academy extensively with my own children and (together with friends) to help kids in Newark, NJ. Khan is much different in practice than what it looks like on the surface.
Khan has lots of bite-sized video lessons that are well-produced (even when you only see a simple blackboard). They range in quality from pretty good (most of the math) to excellent (browsed through some amazing musical theory and social science videos). Khan is judged on the videos, but they're almost besides the point.
Computer-based education is only clearly superior in mathematics only (so far). This is because computers are far better-suited than teachers or books to:


*

*Move at your pace

*Allow guessing before learning to prime you for what's coming

*Provide time-spaced learning to ensure knowledge sinks in

*Check for mastery before allowing you to move forward

*Motivate via gamification

*Probe previously-mastered areas for weaknesses

*Help coaches to check for appropriate progress


The videos, while very helpful, are only a last resort. You should only watch the video after first guessing and then using the written hints. 
Khan is amazing in the areas covered by exercises. Khan is far less effective in subjects with videos but no exercises (higher areas of linear algebra, calc, etc.). I expect Khan to gradually expand their coverage and it already seems like a superior alternative for non-math/engineering majors.
A: I like the videos.  
But I don't think they are what is special about khanacademy: instead it is the combination of the self-study videos together with the machine-graded and assisted  exercises, where a human tutor can monitor progress on the exercises.  In a sense this might be seen as the reverse of traditional education where the tutor teaches and the student does exercises alone.  Time will tell whether it is a better model.    
