An investigation of the machinability of beryllium-copper alloy using two different dielectric mediums and four different working currents resulted in the following data on material removal rate (this is a subset of the data that appeared in the article "Statistical Analysis and Optimization Study on the Machinability of Beryllium- Copper Alloy in Electro Discharge Machining," J. of Engr. Manufacture, 2012: 1847-1861).

a. After constructing an ANOVA table, test at level .05 both the hypothesis of no medium effect against the appropriate alternative and the hypothesis of no working current effect against the appropriate alternative.
b. Use Tukey's procedure to investigate differences in expected material removal rate due to different working currents (Q.05,4,3 = 6.825)?

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Working Current 10 15 20 25 2433 3830 .5625 .7258 Oil Water .1590 .2649 3609 4773