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