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Re: Back to basics – testing your hypothesis.
Posted by:
dsmith (IP Logged)
Date: January 21, 2007 03:40PM
Carl Sagan in his book “The Demon Haunted World: Science as a Candle in the Dark,” suggests that the best method for testing a hypothesis is to try to find ways to make it fail, to work to refute it. Any hypothesis can be supported on the most miniscule amount of evidence and is a process that does not necessarily encourage the search for more.
Finding evidence to only support a hypothesis can lead to erroneous results and a false sense of support. There is a difference in “necessary evidence” (condition) and “sufficient evidence” (condition). There is a good discussion on this is Thomas Gilovich’s book, “How We Know What Isn’t So.” Necessary evidence is that which is necessary for the event to come about. Sufficient evidence is what is necessary to say this is more likely, or conclusively, the reason it is so. Example, if you see burn patterns on a floor, you may correctly hypothesize that the patterns resulted from burning ignitable liquid. (However, this is only one possible explanation.) For you to hypothesize burning ignitable liquids created the pattern, the floor must be burned. This is a necessary condition. However, this is not sufficient evidence to conclude the patterns were created by ignitable liquids. Other hypotheses are also possible, and can be supported on the same evidence. For example,fire fall, localized burning of combustible materials, ventilation effect, the effect of a hot-gas-layer, and post-flashover burning all must be considered as these conditions can also produce burning of the floor. If an ignitable liquid is found in the area, as demonstrated by a positive laboratory test, then you have tested the hypothesis and found “sufficient evidence” to support the claim that the patterns were created by an ignitable liquid. If the lab test is negative, other alternative explanations should be considered.
Necessary v. sufficient conditions can be thought of as “levels of certainty” that we use to make determinations about the world. Necessary conditions can be equated as those which are “possible”, while sufficient conditions we can equate as “probable” (more likely than not or dominant to the others) or in some cases “conclusive” (there can be no other explanation). Occassionally, you end up with a lot of possibilities, but no hypothesis that's probable, or dominant to the others.
Denny Smith
Kodiak Fire & Safety Consulting
6409 Constitution Drive
Fort Wayne, Indiana 46804
260.432.6590 - office