An article in Lubrication Engineering December 1990 describe

An article in Lubrication Engineering (December 1990) described the results of an experiment designed to investigate the effects of carbon material properties on the progression of blisters on carbon face seals. The carbon face seals are used extensively n equipment such as air turbine starters. Five different carbon materials were tested, and the surface roughness was measured. The data are as follows: a) Does carbon material type have an effect on mean surface roughness? Use a = 0.05. b) Apply the Tukey?s method to this experiment.

Solution

We use SPSS to do the analysis

Since all the confidence intervals include 0, there is no difference in the means.

Multiple Comparisons
Dependent Variable: VAR00002 Tukey HSD
(I) VAR00001	Mean Difference (I-J)	Std. Error	Sig.	95% Confidence Interval
Lower Bound	Upper Bound
1	2	.18083	.08297	.189	-.0689	.4305
3	.24250	.09818	.120	-.0530	.5380
4	.31250	.11132	.070	-.0225	.6475
2	1	-.18083	.08297	.189	-.4305	.0689
3	.06167	.09089	.903	-.2119	.3352
4	.13167	.10496	.608	-.1842	.4475
3	1	-.24250	.09818	.120	-.5380	.0530
2	-.06167	.09089	.903	-.3352	.2119
4	.07000	.11734	.931	-.2832	.4232
4	1	-.31250	.11132	.070	-.6475	.0225
2	-.13167	.10496	.608	-.4475	.1842
3	-.07000	.11734	.931	-.4232	.2832