The quality control director for a clothing manufacturer wants to study the effect of operators and machines on the breaking strength (in pounds) of wool serge material. A batch of the material is cut into square yard pieces, and these are randomly assigned, 3 each, to all 12 combinations of 4 operators and 3 machines chosen specifically for the experiment. The results are as follows:
MACHINE
OPERATOR I II III
A 115 111 109
A 115 108 110
A 119 114 107
B 117 105 110
B 114 102 113
B 114 106 114
C 109 100 103
C 110 103 102
C 106 101 105
D 112 105 108
D 115 107 111
D 111 107 110
At the 0.05 level of significance,
a. is there an interaction between operator and machine?
b. is there an effect due to operator?
c. is there an effect due to machine?