During lunch this week an old friend said that during the first gas crisis when the government reacted by slapping a 55 mph speed limit on everything, he did an interesting calculation. Taking the standard numbers then available, he computed how many lives were saved due to lowering the speed limit. Remember the stated reason was to conserve fuel; decreasing the highway slaughter was a welcome side effect.
But then he realized that if you don’t kill as many people, you have more people living. Those living people use energy. If you have more people, you use more energy. It’s rather simple to compute the additional fuel consumption due to the extra people being around. The result is that by lowering the speed limit, we used more fuel.
Because of the demographics, the net increase in fuel consumption would decrease each year the lower speed limits were in place. At 7.2 years after the imposition, society would reach a break-even point after which there would be a small net saving.
Given the raw data, we could argue about his results, but they are indicative of what I have presented many times in this series: if you don’t do the sums right, you get the wrong answer. A corollary is that you should not try to force your opinions on others because you are probably wrong if you didn’t do the sums right.
Without doing any sums at all, the average person will naively agree that forcing a lower speed limit saves energy. That is the politically correct answer. Only it happens to be wrong and not just by that one analysis – there are other factors that make it even more wrong.
This type of analysis is unlikely to change anyone’s opinion about the effect of lowering speed limits because we have been told for decades the speed kills and speed wastes gasoline. If it’s in the newspapers and on television, it must be correct.
And that observation brings us to my trip to the library this week where I picked up from the new books section a delightful surprise, Myths, Lies, and Downright Stupidity by John Stossel of 20.20 fame.
John is a good writer and observant reporter, but he is not a scientist. At least I doubt he would claim to be a scientist. Nevertheless, his reporting is much more scientific and logical than the vast majority of what passes as information.
In his book, he does the equivalent of what my friend did with speed limits. He takes on commonly accepted statements such as “chemical pollution is the cause of the cancer epidemic,” showing that this cannot be true simply because there is no cancer epidemic. Any impression of being in an epidemic is an artifact of increased reporting and early detection. A lot of well-meaning activists do not like to hear that kind of talk, but I love it.
For years I have chaffed at the various calamities or potential calamities that seemingly sane people insist on worrying about. The fact is that we are safer, healthier, and live longer than any of our ancestors. Do you worry about violence in schools? Children are much safer in schools than they are going to and from schools. Many more people die from getting hit by lightning than from being shot in schools. Be concerned about school safety, but keep it in perspective. People have been jailed and charged with heinous crimes against children when even a casual reading of what we purported to have been done to the children showed the charges were nonsense given the time line and space available. It was a modern Salem hysteria with about as much justification.
So why do I write about statistics, probability, and decision theory? Maybe I can convince a few people to simply look at data and question commonly propagated myths before committing to belief. The errors we all make are often harmless in themselves, but when a whole society makes the same stupid mistakes, disaster results. Society has no problem if a person is a creationist, but we all have a big problem if creationism is taught as though it were credible science.
In response to the interest my original tutorial generated, I have completely rewritten and expanded it. Check out the tutorial availability through Lockergnome. The new version is over 100 pages long with chapters that alternate between discussion of the theoretical aspects and puzzles just for the fun of it. Puzzle lovers will be glad to know that I included an answers section that includes discussions as to why the answer is correct and how it was obtained. Most of the material has appeared in these columns, but some is new. Most of the discussions are expanded compared to what they were in the original column format.
[tags]gas crisis, 55 mph, decision theory, Myths Lies and Downright Stupidity, John Stossel[/tags]