January 23rd, 2016
(written by lawrence krubner, however indented passages are often quotes). You can contact lawrence at: firstname.lastname@example.org
You may have had this experience before: You buy two identical articles of clothing. They are the same brand, style and size — maybe even the same color. They are exactly the same except that one fits, and the other does not. The problem is manufacturing variance.
To test manufacturing variance, we measured 20 identical new t-shirts. These shirts were priced in the $20 range. The graph below depicts the distribution in chest width and length, which each have a standard deviation of about one fifth of an inch.
It’s probably more helpful to think about the size of a particular of shirt as a distribution, rather than an exact number. Maximize your chance of success as a consumer by buying t-shirts where the average produced is a very good fit. This way only extreme outliers won’t fit you very well.