An experiment is run on an operating chemical process in which four variables are changed in accordance with a randomized factorial plan:
(a) Make a table of plus and minus signs from which the various effects and interactions could be calculated.
(b) Calculate the effects.
(c) Assuming three-factor and higher order interactions to be zero, compute an estimate of the error variance.
(d) Make normal plots.
(e) Write a report, setting out the conclusions to be drawn from the experiment, and make recommendations. (Assume that the present conditions of operation are as follows: 1 = 5%, 2 = 40%, 3 = 10 rpm,. 4 = l80°F.)
(l) Show pictorially what your conclusions mean.