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G. Moore
G. Moore

Reputation: 19

Human-chosen pseudo random variables that are not really random?

We're all familiar with not really random, human-chosen variables such as the disproportionate appearance of 37 when humans are asked to choose a number between 1 and 100, and for other cases (disproportionate selection of a particular one of four quadrants of a 2x2 grid, etc). I'm sure I'd once read that these are called "[something] Variables."

Can anyone please provide me with the term for these variables? Many thanks!

Upvotes: 0

Views: 43

Answers (1)

pjs
pjs

Reputation: 19855

Random behavior is described by probability distributions. The Uniform(0,1) distribution is particularly important in computing because we have a variety of techniques to transform U(0,1)'s into other distributions. It's also easy to transform independent observations into non-independence via distributional conditioning. I don't know of any general solution to go the other way. Bottom line is that it's much easier to deal with independent uniforms.

Because of those two observations, the gold standard for Pseudo-Random Number Generators (PRNGs) is to produce uniformly distributed values which appear to be independent. (I say "appear" because if each value follows its predecessor based on deterministic calculations, clearly they must be dependent in some fashion.) Humans do a terrible job in both regards. To actually answer your question, values chosen by humans can be described as "non-uniform" and "not independent."

Some people might be tempted to say "uncorrelated" rather than "not independent," but they're not the same thing. While independence always produces zero correlation, there are counter-examples where dependent random variables can have zero correlation. In fact, most PRNGs are pretty good at producing uncorrelated values.

Upvotes: 1

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