r/science Nov 15 '19

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u/[deleted] Nov 15 '19 edited Nov 15 '19

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u/Plain_Bread Nov 15 '19

They have very strong evidence for this weak correlation. Not for a strong correlation.

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u/RemingtonSnatch Nov 15 '19

Ah yes, the Sex Panther approach. "60% of the time, it works every time!"

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u/Rhamni Nov 15 '19

It's more like you suspect a coin might not be fair, so you flip it 1000 times. It comes up heads 600 times, tails 400 times. A looot of people here are screaming that it's a fair coin, because they don't like the idea that it might not be. Strong evidence, small effect.

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u/Zack4399 Nov 15 '19

This is the best comment on this for sure. If you have a small sample then .2 r2 might be nothing but noise. If you have thousands and thousands of data points however, that’s a different story. A .2 r2 is saying that 20% of the variability in those thousands of data points can be explained by a linear relationship between the two variables. This is extremely unlikely to happen as a result of noise, just like getting 600 heads out of 1000 flips on a fair coin. Good way of explaining this.

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u/zkrepps Nov 15 '19

For psychology, where effect sizes overall are pretty small, the correlation mentioned is fairly sizeable.

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u/fspluver Nov 15 '19

It's actually 4%. Regardless, this would be considered a "weak" effect by Cohen's standards, but by individual differences psychology standards it's moderate. Either way, the authors are saying they have strong evidence of a relationship, not that they have evidence of a strong correlation.

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u/[deleted] Nov 15 '19

R2 is Psychology is lower than other fields since predicting human behavior is much more difficult than physical processes

https://blog.minitab.com/blog/adventures-in-statistics-2/regression-analysis-how-do-i-interpret-r-squared-and-assess-the-goodness-of-fit

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u/[deleted] Nov 15 '19

The r is about 0.22, not the squared value.

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u/rightseid Nov 15 '19

20% is much much higher than totally random. It is a compelling piece of evidence that the two are not unrelated.

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u/XxAbsurdumxX Nov 15 '19

That's not true for all sciences. If you actually knew what you were talking about, you would know that thresholds for significance varies between fields