Question

In the Plackett-Burman method, the evaluation of x-1 variables by x experiments, where x must be the multiple of?

(a) 2

(b) 4

(c) 6

(d) 8

The question was asked in my homework.

This is a very interesting question from Medium Optimization in section Introduction to Fermentation Processes & Media for Industrial Fermentation of Bioprocess Engineering

Answer 1

Right choice is (b) 4

Easy explanation: The Plackett-Burman method allows for the evaluation of x-1 variables by x experiments, x must be a multiple of 4, e.g. 8, 12, 16, 20, 24, etc. Normally one determines how many experimental variables need to be included in an investigation and then selects the Plackett-Burman design which meets that requirement most closely in multiples of 4.