Consider the data from Exercise 14-20.

(a) Construct the design that would have been used to run this experiment in two blocks of eight runs each.

(b) Analyze the data and draw conclusions.

Exercise 14-20

An experiment described by M. G. Natrella in the National Bureau of Standards€™ Handbook of Experimental Statistics (1963, No. 91) involves flame-testing fabrics after applying fire-retardant treatments. The four factors considered are type of fabric (A), type of fire-retardant treatment (B), laundering condition (C€”the low level is no laundering, the high level is after one laundering), and method of conducting the flame test (D). All factors are run at two levels, and the response variable is the inches of fabric burned on a standard size test sample.

The data are:

= 40 30 (1) 42 = 31 45 ad bd abd 50 = 29 39 ab = 40 cd