Sample Size? Who needs an appropriate sample?

Last year, I spent a lot of time talking about statistics and the need for analysts to understand this important science. Ive written a lot about the need for appropriate samples, especially around the idea of supporting a determination of "match" or "identification."

Many in the discipline have responded essentially saying, it is what it is - we don't really need to know about these topics or incorporate these concepts in our practice.

Now comes a new study from Sophie J. Nightingale and Hany Farid, Assessing the reliability of a clothing-based forensic identification. If you've been to one of my Content Analysis classes, or one of my Advanced Processing Techniques sessions, reading the new study won't yield much new information from a conceptual standpoint. It will, however, lend a bunch of new data affirming the need for appropriate samples and methods when conducting work in the forensic sciences.

From the new study: "Our justice system relies critically on the use of forensic science. More than a decade ago, a highly critical report raised significant concerns as to the reliability of many forensic techniques. These concerns persist today. Of particular concern to us is the use of photographic pattern analysis that attempts to identify an individual from purportedly distinct features. Such techniques have been used extensively in the courts over the past half century without, in our opinion, proper validation. We propose, therefore, that a large class of these forensic techniques should be subjected to rigorous analysis to determine their efficacy and appropriateness in the identification of individuals."

The important thing about the study is that the authors collected an appropriate set of samples to conduct their analysis.

Check it out and see what I mean. Notice how the results develop from the samples collected. See how they differ from an examination of a single image. Thus, I always say, under a certain sample size, you're better off flipping a coin.

If, after reading the paper, you're interested in increasing your knowledge of statistics and experimental science, feel free to sign-up for Statistics for Forensic Analysts.

Have a great day, my friends.