How random can you be?

[timosman]

https://www.expunctis.com/2019/03/07/Not-so-random.html

Mar 07, 2019

Let’s play a game. You press ← and → as randomly as you can, and I will try to guess your next input. Use your keyboard or the buttons below (on touchscreen devices).

Every time I guess right, I will take $1 from your virtual account. Every time I guess wrong, you’ll get $1.05. If you are as random as you think, you’ll be making virtual dough in no time. Don’t worry, there is no cheating involved. I simply keep track of the patterns you produce and use them to predict your next move.

Once you’ve become tired of watching your virtual money evaporate, press the “randomize” button below, and I will add 10 pseudo-random inputs on your behalf. On average (i.e. not all the time), this is going to earn you some money. Isn’t it ironic that a pseudo-random number generator is more “random” than you are?

...

 

So how does it work exactly? Your fingers tend to repeat certain patterns even if you don’t notice it. The program keeps a database of each possible combination of 5 presses, and two counters are stored under each entry — one is for every zero that follows the combination, and the other one is for all the ones that follow this combination. So every time you press a key, an entry in the database gets updated. To make a prediction, the program needs only to look up the entry corresponding to the last 5 presses and decide by looking at the counters which key press is more likely to follow. The rest is up to Fortuna (velut luna). I’ve run this script with 200 pseudo-random inputs 100,000 times, and found that the distribution of correct guesses is approximately normal with µ=50% and σ=3.5% (this agrees with the binomial estimation, of course). The probability of the program guessing your inputs >57% (µ+2σ) of the time purely by chance is very slim, which suggests that you really aren’t good at making random choices.

[Swordsmyth]

https://www.expunctis.com/2019/03/07/Not-so-random.html

 

People are creatures of habit, it takes a lot of work to learn to be random.