The Use and Misuse of p Values
May 30, 2013
The article Friends Don’t Let Friends Calculate p-values (Without Fully Understanding Them) on The Scottbot irregular blog is about p-values, the probability of a statistic being significant. The danger of misuse of p-values is the point of the article. Wikipedia lists 7 typical ways p-values are misrepresented, including Lindley’s paradox and the prosecutor’s fallacy. The blog uses the example a coin toss to explain further.
“Calculating how often 10 coin-tosses of a fair coin will result in a 7/3 split (or 8/2 or 9/1 or 10/0) will give you a different result than if you calculated how often waiting until the third tails will give you a 7/3 split (or 8/3 or 9/3 or 10/3 or 11/3 or 12/3 or…). The space of possibilities changes, the actual p-value of your experiment changes, based on assumptions built into your experimental design.”
What is not mentioned in an experiment can be incredibly significant, and that makes it possible for people to manipulate data into saying very different things. If you are interested in p-values, you should certainly read this article in its entirety, and then go back and check your math and your assumptions.
Chelsea Kerwin, May 30, 2013
Sponsored by ArnoldIT.com, developer of Augmentext
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