Friday, October 26, 2012

Science Term of the Week: Null Hypothesis

Science is often (incorrectly) defined as a group of facts. This isn't the case at all. Instead, science is a system used to analyze the universe. You've probably heard of the scientific method, and I can guarantee if you read this blog any longer you'll hear much more about it. In this week's Science Term of the Week I wanted to focus on the term hypothesis. Specifically, the Null Hypothesis, which is written "H0". 

The first step when you are approaching a problem scientifically is to define the Null Hypothesis - the default position. One way of thinking about the Null Hypothesis is assuming that nothing is significant or that nothing has happened. Two examples of the Null Hypothesis are:

  • A new drug is proposed for treatment of a disease. The Null Hypothesis is that the drug has no effect.
  • Reports have come in that a UFO has been spotted by Roswell, New Mexico. The Null Hypothesis is that the unidentified object is nothing significant (it is not an alien ship).
 The Null Hypothesis is an important concept in science, and it can never be proven. It can be rejected (the drug has an effect) or fail to be rejected (the drug has no effect). The important difference between proving the Null Hypothesis and failing to reject the Null Hypothesis is that any one test (or any group of tests, no matter how large) is not enough to prove a negative.

The Null Hypothesis is the reason I can say things like homeopathy has no effect, essential oils have no medicinal value, and Roswell aliens don't exist. Without the Null Hypothesis a test that gives negative results gives no information and could be considered "failed". With the Null Hypothesis, even negative results are meaningful.

So next time you have a question - define a Null Hypothesis and put it to the test!

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