# What’s So Funny About Correlation? xkcd.com. What is Correlation? When two things go together: cookies & milk macaroni & cheese peanut butter & jelly.

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What’s So Funny About Correlation? xkcd.com

What is Correlation? When two things go together: cookies & milk macaroni & cheese peanut butter & jelly

What is Statistical Correlation? A mutual relationship between two variable quantities. Correlation coefficients measure how closely related the two variables are. Stronger relationships mean that a change in one variable is accompanied by a systematic change in the other. Correlation CoefficientStrength 1Perfect Positive 0.7 to 0.9Strong Positive 0.4 to 0.6Moderate Positive 0.1 to 0.3Weak Positive 0No Correlation -0.1 to -0.3Weak Negative -0.4 to -0.6Moderate Negative -0.7 to -0.9Strong Negative Perfect Negative

Does the amount of uranium stored at nuclear plants correlate with the amount of power they generate?

YearUraniumPower 1984160.2327.6 1985153.2383.7 1986144.1414 1987137.8455.3 1988125.5527 1989115.8529.4 1990102.7576.9 199198612.6 199292.1618.8 199381.2610.3 199465.4640.4 199558.7673.4 199666.1674.7 199765.9628.6 199865.8673.7 199958.3728.3 200054.8753.9 200155.6768.8 200253.5780.1 200345.6763.7 200457.7788.5 200564.7782 200677.5787.2 200781.2806.4 200881.9806.2

Does the amount of uranium stored at nuclear plants correlate with the amount of power they generate? www.tylervigen.com

Does the amount of uranium stored at nuclear plants correlate with the amount of power they generate?

-0.89905

Why might the amount of uranium stored at nuclear plants correlate with the amount of power they generate?

What is Causation? The action of causing something; the relationship between cause and effect. Smoking causes cancer Sugar causes cavities Gravity causes objects to fall

What is Causation? We can make an inference about a causal relationship based on the strength of correlation. We have to be careful about assuming an actual causal relationship, though.

How does consumption of chicken correlate with crude oil imports?

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How does consumption of chicken correlate with crude oil imports? YearPer capita chicken consumption (lbs.) Total crude oil imports (millions of barrels) 200054.23311 2001543405 200256.83336 200357.53521 200459.33674 200560.53670 200660.93685 200759.93656 200858.73571 2009563307 Chicken data from USDA. Oil data from Dept. of Energy.

How does consumption of chicken correlate with crude oil imports? 0.9

How does consumption of chicken correlate with crude oil imports?

Does eating more chicken cause crude oil imports to increase? ?

But wait… …if eating more chicken doesn’t cause crude oil imports to increase, then why are they so closely correlated? ?

The Lurking Variable Total US Population Year

Correlation and Causation Correlation is a measure of how well data fit a relationship. A correlated relationship between two quantitative variables is not the same as a causal relationship. Causal inferences about correlated events can be made based on underlying theories and knowledge. The determination that one thing causes another requires a scientific experiment.

"Correlation is not causation, but it sure is a hint.“ Edward Tufte, American Statistician

What’s So Funny About Correlation? Cartoon from xkcd.com

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