INTRODUCTION

INTRODUCTION: This blog is my effort to help improve the understanding of numbers, especially as used by the press and in research reported by the press. I hope journalists will find it useful to improving the quality and validity of what they write. The topics are chosen from items I encounter with depressing frequency, in which failure to understand what they are saying or reporting leads journalists to write material that may mislead the public and result in ill-advised policy decisions. Please understand that my comments do not reflect my opinions of the subject matter. I protest misleading information even when it supports my opinions.

Thursday, September 6, 2012

The Demon "Percentage" - #1

Percentages, although often very useful, are also easily misunderstood.  This is a recurring theme.

I recall reading an article that compared the accuracy of voice recognition programs.  It compared one that was 97% accurate to another that was 99% accurate, and concluded that the two weren't very different in accuracy.  While it's true that 97 and 99 are in general not too different, they are very different as percentages: one means 3% errors and the other means 1% errors!  The 1% error rate program is far more accurate than the one with a 3% error rate.
Remember to think about percentages along with their opposites, especially when close to the 0% and 100% extremes.
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