04 May 2010

Regression

A study titled The largest Last Supper: depictions of food portions and plate size increased over the millennium has attempted to extrapolate nominal meal portion sizes from paintings of The Last Supper created over an 800-year span. Now, tell me if this is not the worst regression analysis you've ever seen:

Really, a parabolic fit? One that extends 300 years beyond the range of the data? I'm no expert in regression analysis, but even an r-value of 0.5 does not seem worthy of the strong conclusions which the article draws.

Aside from the poor correlation coefficient, and assuming the very method of linking plate-to-head ratio to portion size is valid, it looks like their extrapolation hinges entirely on one outlier (the most recent painting) and a century of plenty (in the 1500's, where there were not only small portions but large portions). This is a crock.

3 comments:

Mike said...

How does this account for the well-known phenomenon of human beings' heads getting smaller with time?

Seth said...

If I had authored the study, it would have assumed some other object as constant and measured the correlation between time and pretension.

Mike said...

Can you edit the draft of my article I'm submitting to Science, "The quality of regression curves occurring in high-rated research journals on the topic of quantitative nutritio-artistic criticism, with analysis of the effect of absurdly long academic titles"? Also, if you could find a way to work "nano" into the title, your aid would be appreciated, Alot.

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