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## Friday, January 3, 2014

### independence^correlation btw 2 rand vars, my take

I feel correlation is more  a statistics concept, less a probability concept. In contrast, Independence has 2 interpretations -- in prob vs stats -- see other posts in this blog.

In a theoretical model, the color vs the points on a random poker card are independent, so out of 9999 trials, the data collected should show very very low correlation, but perhaps non-zero correlation!

From this example, I feel in a theoretical model, correlation isn't important. However, in real world statistics, correlation is probably more important than Ind. As described in other posts, I feel ind is shades of grey, to be measured ... using correlation as the measure.

Whenever someone says 2 thingies are independent, i think of a logical, theoretical models (probabilistic). In the real world, we are never really sure how true.

Whenever someone talks about correlation/covariance, i think of statistics on observed data.

It's well known that 2 uncorrelated variables may be dependent.

Many people prefer to day "A and B are uncorrelated" when they really mean "they don't depend on or influence each other". I feel most of the time the meaning is imprecise and unclear.