The Great Extrapolation

Science is so frequently abused it is no wonder that people are rapidly losing their trust of anything with the label science. I suppose this is the just end for those who used the science label and the trappings of science, graphs, charts, R2 values, big words, to trick people who rightfully trusted science. Science, real science, is a method to discover the truth about the world. In this system it is acceptable to make extrapolations and theories that are difficult or even impossible to prove. This creative side of science gives scientists and people ideas to test, and if real science is being done, discard if they are found in contradiction of observation. As a result, any theory that cannot be tested is in essence not science.

One of the most common features to the ‘sale’ of pseudo-science and loony conspiracy theories dressed up as science is the graph; specifically the false extrapolation graph. Here, I think, is a perfect example of what I mean. When I was small, my mother and father kept track of my height at different ages. When I plot this data against my age in years, the resulting graph is below.

As you can clearly see, my growth between age 11 and age 14 was really nicely correlated to my age, that’s a nice statistical correlation.. so lets extrapolate.

OK, so for anyone with even my sister’s level of math, the 12.779 inches at age 0 wasn’t a surprise, it is from the equation for the line. (My sister is a very talented violinist, who would probably have been good at math too if she had liked it at all.) But lets extrapolate into the future the same amount.

That puts me at around 120 inches next year! I should warn my wife that I am about to grow four feet. Alright, so this example is obviously ludicrous. How about an example of potential pseudo-science? Here is a graph of IPCC models (from the IPCC website, some random presentation linked if you click on the slide.)

I am not (here at least) trying to make the case that man-made global warming is a total hoax brought to you by the same set of people that gave us the ozone hole… However, it is a particularly good rule of thumb that if a theory asks you to believe a prediction of the future based on past measurements, you should be skeptical. In fact, people should at all times, and in all ways, be skeptical of all claims made by all people. Since the most reverend and ancient ploy to convince people to believe or buy something is appealing to an authority you made up for the purpose it is even more important to be skeptical of any ‘authority’… not stubborn disbelief, nor unfettered belief, just skepticism. A good non-scientific example: Obama wants us to believe the authority of a non-partisan study conducted by a donor to his campaign…

Well, as one last note, here is how the information on my age to height is potentially valid. When I was 12.7 years old, I was probably quite close to the 68.45 inches predicted by the linear fit on the graph. That is, the correlation is only valid inside the range of measurements. Perhaps mind is all polluted by analytical chemists in college 🙂 and that makes me demand my correlations be within the measured standards. (Read Wikipedea on Standard Curves… I don’t feel like explaining it now.)

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2 responses to “The Great Extrapolation

  1. For the record The Dusty Thane was 18 inches at birth.

  2. Pingback: Science Abuse | The Dusty Thanes

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