Test driving the Khan Academy: how I learned to use conditional probabilities and combination

I have been hearing good things about the Khan Academy - an impressive online education effort spawned by American computer scientist Salman Khan trying to tutor his cousin through screen capture videos. Khan has since quit his job in finance, is generously funded by Google and others and attracts 3.5 million monthly users. This mission is a test drive of KA as an education institution.

I picked the above video on Conditional probability and combination (watch it in the KA website for Q&As and goodies). I picked this because:

  • math is the traditional area of strength of KA, and a traditionally badly taught topic in many countries including mine.
  • probability theory is a very interesting and useful part of math, but many, myself included, find it counterintuitive and need to make a conscious effort to teach themselves to think in probability conditional probability is a topic I have been taught at university, but that I am not at all confident with. This means I can compare classroom teaching with KA, while still needing to learn the damn thing.

How I did it

So how do you watch a video of a math lecture on the Internet? I armed myself with notepad and pens, just like in a normal classroom, and opted for a very active approach: this is math, and I like to scribble, not just to listen. As I dived in:
  • I made extensive use of the pause button. Remember how you would scramble to keep up with the teacher? How you would need to make real-time decisions of whether to sit back and listen carefully (helps understanding) or scribbling frantically (helps memorizing) at any given time? That’s gone in KA. You can do both: you listen, pause the video and write down your notes. Missed something? No problem, just backtrack. The video never gets tired of repeating, so you can replay it until you get it right.
  • I took my time, and as a result spent about 30 mins to go through the video (which is only 17 mins), while still going through all the steps myself and checking that I was getting the same results as the teacher. That’s super-cost effective, given that I am going through an example problem that combines conditional probability and combinatorics, with a great final two minutes of exploring the intuition of it at the end; and given that I spent no time at all traveling to a classroom. I guess that the one- or two-hour lessons we are accustomed to are the result of constraints imposed by the adoption of the classroom technology: teachers and students need to get there, take off their coats, take out their notes, find seats etc., and 15 mins are gone. At this point, you try to make the most of it by spending 40 to 100 minutes actually lecturing. KA videos use the topic, not the hour as a unit; most are 6 to 12 minutes long, at least in math.
  • what about questions? You can ask them in the comments. And people do, and other people answer them. The quality is amazing! Here’s your peer-to-peer element in KA.
  • gamification: KA awards points and badges for taking lessons, asking and answering questions. I got a “Nice Listener” badge for Probability because I watched more than 15 minutes of video in the same topic. :-)
  • added goodies: there are transcripts for the whole lecture; the community is also involved in sharing notes and creating the subtitles in different languages


Full success. Need to impress a girl with conditional probability and combination? I’ve got you. Most importantly, if I should forget it and need it at some point in time, I know where it is, and I can refresh it in half an hour. And, man, Khan is an outstanding teacher. For the kind of learner that I am, this is way, way better than school, or even university.

ok, I’m in

I´ll give this a try.  I have to revise this stuff and this is a way better setup for me. I hated the stats and probability classes at uni because if you blinked an eye you were lost. And 45x2 minutes of this stuff seemed serve as fuel for my brain to think about everything and anything else. Plus we had an aggressive lecturer who I suspect hated having to teach clueless students as part of his PhD requirements and really gave you a hard time if you dared ask a question. Will get back to you once i´ve done one of the classes too :slight_smile:


Now that’s something


Now that’s something they won’t teach you in my school, except the very basics of probabilities, and in a completely unstructured way. I’m taking up coding with Codecademy, it seems easy and fun, so I will be back soon with a report on my own… I looked up something easy to get me started, but I wonder if online learning is useful if one takes a one crash course in a topic, or we should instead make it part of a larger effort to systematically study and gain more in-depth knowledge?

For smth you have a strong background in, one course is probably enough, but other than that I don’t think so. What about the self- discipline you have to put in to embark on a truly rewarding experience? In the end, even if you have nice visual support and content delivered so that it’s interesting, I tend to think it’s still harder than it seems, and it can only replace tiny bits of the learning experience in school.

-will get back to you with new insights once I complete my course

What about people with short attention spams, does this really work better than just sitting in a classroom?

Never enough!

One course is never enough, in any learning environment, is it? You do arithmetic in primary school, then geometry, then algebra around age 11, and on it goes, until you find yourself in number theory and you are actually proving the theorems that power 2+2=4.

Having said this, I would not underestimate unstructured, DIY learning. There is much pleasure in saying “what the hell, I’ll just take five lessons in planetology and figure out later what they are for”.

Taking up coding, huh? :slight_smile: Any language in particular?

I agree Alberto…

Yes what

I agree Alberto…

Yes what language you are learning Noemi? does it work so far?

I am learning HTML and CSS as I think one way or the other at some point they are both very useful for blogging, newsletters and facebook tabs… :slight_smile:

Codecademy started out with Javascript only, now I think they’re expanding and also looking for instructors. I’m only at the basics, and again the self discipline is killing me. So hard to do something just for yourself, if nobody tells you to  :slight_smile:  I know it’s weird, duties come first .

Also, I asked my sister (she’s a programmer) to teach me more html and css, and for now I’m glad  I know the difference between those 2… and keep learning by doing, such as with wordpress.

PS in a different life I would’ve made an excellent programmer, actually I was programmed to do that - with dad being anengineer and mom teaching computer science, and having loved the logic behind it and behind maths and stats, but I guess what you choose is what really defines you. So for me flirting with these, if only I had more time, gives me a bit of sense of “what would have been like if…”?

just started to try it!


I started watching it and it’s quite amazing!! Actually it is very explaining and understandable and I never thought I could remember a single thing afterwards…but NO! I am able to remember a lot and I even looked for probabilities tests and problems to solve :slight_smile:

I wish I had watched it before giving for my Maths exams in the uni in which I did quite bad…

In general I am very into virtual tutorials and I have done some practise with W3Schools for coding and some design tutorials with Lynda.com. I think it has a lot of advantages as money and time saving, you do it on your place just from your sofa, you take your time and your confy. Sometimes specially with Maths and Physics courses I felt that I needed more time to digest and harvest the information than given time and I couldn’t have it…

I will get back when I have more experience testdriving it


link doesn’t work

By the way the link of (watch it in the KA website for Q&As and goodies) doesn’t work to me…:frowning:


Thanks for this, Luna. I fixed the broken link.

Features like pausing and replaying are excellent examples of benefits that exist for digital and pre-recorded learning resources that are not usually offered in a situated learning environment - some students use dictaphones to gain this advantage from traditional lectures, and OU videos on BBC2 (back in the day…) also allowed this.

When students use KA’s excellent video commenting services to ask or answer questions related to a video, this actually adds value to the resource (where we consider the resource to be the full page with embedded video and comments, rather than the video alone).

It’s a good example of collaborative answer-finding and peer-review (upvoting) adding value to an existing resource with little additional cost to the original resource provider. The use of up-voting & down-voting to improve answer-finding (specifically) is proven to be effective in the real world by excellent and long-running sites such as those in the StackExchange family; in concert with a context (the video), this is a force to be reckoned with. I think that this is the kind of thing that will constitute a ‘digital future’.

Interesting comments on using the topic and not the hour as the unit. In a traditional lecture, there is a need for the lecturer to ‘fill their slot’ exactly to the allocated time for which they have the lecture theatre. I think to have this need removed is likely to be of benefit to the lecturer and to improve lecture quality (and also student attentiveness :wink: ).