A manufacturer of television sets is interested in the effect ontube conductivity of four different types of coating for colorpicture tubes. A completely randomized experiment is conducted, andthe following conductivity data are obtained:
Coating type | | Conductivity | | |
1 | 143 | 141 | 150 | 146 |
2 | 152 | 149 | 137 | 143 |
3 | 134 | 136 | 132 | 127 |
4 | 129 | 127 | 132 | 129 |
a) Is there a difference in conductivity due to a coating type?Use ?= 0.05.
b) Estimate the overall mean and the treatment effects.
c) Calculate a confidence interval with 95% for the averagecoating type 4 and calculate the confidence interval with 99% forthe difference between the average coating types 1 and 4.
d) Test all pairs of means using the Fisher LSD method with ?=0.05.
e) Use the graphical method discussed in section 3-5.3 tocompare the means. What is the type of coating which produces thehighest conductivity?
f) Assuming that coating type 4 is currently being used, whatwould you recommend to manufacturer? It wants to minimizeconductivity.
g) Analyze the residuals and draw conclusions about the adequacyof the model.
