A manufacturer of television sets is interested in the effect on tube conductivity of four different types of coating for colour picture tubes. The following conductivity data are obtained.
Coating Type Factor A Factor B Conductivity
1 Low Low 143 141 150 146
2 Low High 152 149 137 143
3 High Low 134 136 132 127
4 High High 129 127 132 129
(a) Using a contrast test if the effect of factor A the same for each level of factor B.
(b) Construct the ANOVA, and test
i.if there any significant difference among treatments.
ii.if the interactions parameters are significantly different from zero