Show-Z-Minx: A note on code lettering.

9 of the 26 letters of the alphabet can be read upside down as well as right side up. The use of these letters as code designations in blind product testing can have a significant effect upon respondents' perceptions of the product, particularly when there is the possibility of settling or separation. An incident is reported in which the use of one of these letters had the effect of introducing irrelevant sources of variance into a product test of a packaged dry food. (PsycINFO Database Record (c) 2010 APA, all rights reserved)