*Guest blog by Ray Schleck. *
What is Khan Academy?

Khan is a website. Free.* It’s best known for it's library of videos, made by its founder, Sal Khan. The videos are simple: just a black screen with Khan’s voice in the background. As he talks, his writing appears. That’s it. You never see him, no animations, no video footage. Each 5 to 10 minute video covers one concept, like ‘ordering fractions’ or ‘calculating slope of tangent line using derivative definition.’

While Khan is best known for videos, I’ve mentioned before: the real action is actually their *math problem sets*. Not the videos. There’s an exercise module for each of the hundreds of math aims (currently, 401) from basic addition to calculus. Think of these like a live worksheet. They are valuable without the videos. Some critics don't like the videos. Are there critics who don't like the problem sets? Not sure.

Let’s say you want to practice simplifying fractions. You can either type "simplifying fractions" into their search bar, or go to the "concept map." This is a map.

So let’s say you click on fractions and then get to ‘simplifying fractions’. This pops up:

In the center is the problem you need to solve. 24/84.

When you have an answer, you enter it into the answer box on the right.

If you’re correct, a little smiley face will pop up and a new problem will appear.

If you’re wrong, the box will shake and you’ll have to try again. You can’t get to a new problem until you put in the right answer. Might take you 10 tries before you get it, but you can’t move on until the right answer goes in the box.

* * *

When You’re Stuck

a)Hints

There’s a red ‘hints’ button located below the answer box. Every time you click it, a new hint will pop up below the problem. Each hint is the next step to solve the problem you’re working on. The very last hint reveals the answer.

b)Video

Below the hint button is the video corresponding to that aim. Couple notes here: the video is the intro lesson to that aim, along with an example or two. It won’t show you how to solve the exact problem you’re working on. Also, once in a while there isn’t a corresponding video, and sometimes there’s more than one listed.

**Four features of these problem sets:**

**1. Remembering You**

From a student point of view, Khan keeps track of all your answers. It tells you when you’ve earned ‘proficiency’ on the aim and suggests which modules to try next.

From a teacher perspective: you can see for all students: what they’re struggling with, what they’ve accomplished so far. You can look into each individual problem to see which wrong answers they were plugging in, how many hints they used, whether they watched a video, and how many seconds passed between every action.

**2. What is “right?”**

Khan only considers your answer ‘right’ if you put in a correct answer on the first try with no hints. Remember, you can’t go to the next problem at all until you plug in the right answer, so you’ll have to eventually find the right answer. But if you mess up even once, or if you ask for any hints, Khan doesn’t recognize any progress towards showing mastery.

**3. What is "proficiency?"**

Khan used to require ‘streaks’ of 10 right answers in a row. Once you hit your tenth consecutive right answer, you were proficient.

Two problems:

a. People got frustrated if they had a streak of 9, made a small mistake, then had to start all over.

b. Khan found if a user made many mistakes at first, a streak of 10 correct still wasn’t enough to keep them retaining the skill into the future.

Now there’s an elaborate algorithm that grants proficiency only once Khan determines you have a 95% chance of getting the next problem right. They developed the algorithm using data from the patterns of right answers they saw amongst their millions of users.

So now, get the first 5 in a row right and you’re done. But if you get the first couple wrong before you figure it out, you’ll have to get around 10 right to pass. If you get one wrong, then get 8 right, then get one wrong again, you don't have to do another full 10 in a row to pass, more like 6-7. But say you get 8 of the first 9 wrong. Then you'll have to do 14 to 15 right to pass.

**4. Incentives**

There are a bunch of points, rewards, and badges that you can earn. Some of for speed, some for mastering a certain number of aims, some are for contributing to a discussion board. They’ve got rewards for anything you can think of and lots of different ‘levels’ of rewards based on how hard they are to earn. For some people, the video-game like rewards -- even if they have no real "value" -- are motivating.

Tomorrow: I'll compare how these 6 Match kiddos did when tutors used Khan Academy to replace Accelerated Math.

*Khan itself is free. Accelerated Math is not. However, the total cost of "Khan usage" may be much higher if, in order for kids to use it, the school has to add many computers for kids to use.