Best of Mind Your Decisions 2011

I posted a lot more this year than in others, so I figured it would be fitting to have a recap of the year’s best posts.

Here are some posts from 2011 that you might have missed and are worth a second look. Most of them are puzzles, which happened to be a very popular addition to the site. Enjoy.

1. Repeating One Digit May Actually Improve the Security of Your Phone’s 4-Digit Lockscreen PIN. I posted this with the bad title “Game theory and probability on iPhone passwords,” but someone over at HackerNews came up with the much better title (thank you), and so the article got picked up by LifeHacker. This was inspired by a phenomenon my friend noticed in which passwords could be easily identified by “smudge marks” on iPhone screens.

2. One mile south, one mile east, one mile north puzzle. This is a brain teaser that Microsoft used to ask during interviews. The answer is a lot more complex that it originally seems.

3. Broken sticks puzzle, and a seemingly paradoxical ratio. This is a puzzle that involves some higher level-math. But if you can set up the equations properly, then the computational search engine WolframAlpha can do the rest.

4. Puzzle: escaping a thief. This problem is a pursuit and evasion game that was also used as a technical interview question.

5. Birthday laws probability puzzle. As I write this list, I find that each puzzle seems to involve a different area of math. The other top puzzles were about geometry, calculus, and physics whereas this one is related to probability.

6. How to reduce employee theft without nagging: 4 tips from behavioral economics. I wrote this article after one of my friend’s was insulted by what he perceived as a petty request from his employer: don’t steal from the postage meter. The employer move was understandable, but it brought about bad feelings as my friend thought of all the unpaid overtime and sacrifices he made to the company. The lesson: be nice and use nudges when delivering warnings. There are more effective ways to reduce theft than nagging.

7. Puzzle: how would you divide the land equally? (spoilers). This is not a hard puzzle, but it got popular because of an interesting extension. The result is an example of mathematical art, and I thank V Paul Smith for generating the beautiful image. It’s something you should not miss.

Also, here are some articles from previous years that still get a lot of traffic:

1. Hotelling’s Game, or Why Gas Stations Have Competitors Nearby. This is one of my earlier game theory articles that has a lot of diagrams to illustrate the ideas.

2. Game theory in the Dark Knight. This is one of the most popular articles on this site. Everyone loved the Batman movie, and its connection with game theory.

3. 16 fun applications of the pigeonhole principle. I was happy to see that this article has maintained in traffic–I love it that some of my math articles are useful to people. This is one of those articles I wrote because I was surprised no one else had written it before, and it could help in teaching the very useful pigeonhole principle.

4. What is the difference between APY and APR?. This article came out of my own curiosity when I was checking interest rates on a savings account. The company advertised both APY and “interest” rates (APR) and I was able to show how the two are related.

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Thanks for all of your support/emails/comments this year. I look forward to next year which will no doubt be filled with plenty of puzzles, game theory articles, and saving advice.