A J shaped distribution is a probability distribution in the rough shape of the letter J placed on its side, or its mirror image. These distributions tend to have some observations at one end, very few in the middle, and a large number at the other end.
J Shaped Distribution Example
Product reviews are an example of a J Shaped distribution: the distribution of product reviews (e.g. on Amazon) frequently shows many ratings are 5-star, a few are 1-star (or vice-versa), and a handful are in between— (Hu & Zhang, 2009).
Terminology Problems with “J shape”
Statistical Problems
Aside from font problems, Hu & Zhang note that the J-shaped distribution “…creates some fundamental statistical problems.” The mean, a common statistic used for calculating future sales, product quality, consumer satisfaction and other metrics only works for unimodal distributions (distributions with one “hump”). The J-shaped distribution is bimodal (two humps); when a mean is calculated from a bimodal distribution, it essentially becomes meaningless. For example, a collection of 1 and 5 star ratings gives a mean of 3 stars— which is not a good reflection of reality.
References
Hu & Zhang, (2009). Overcoming the J-shaped distribution of product reviews. Communications of the ACM – A View of Parallel Computing CACM Homepage archive. Volume 52 Issue 10, October. Pages 144-147. Retrieved December 8, 2017 from: https://dl.acm.org/citation.cfm?id=1562800
Wikipedia (2017). Typeface anatomy. Retrieved December 8, 2017 from: https://en.wikipedia.org/wiki/Typeface_anatomy