Integrated circuits are manufactured on silicon wafers through a process that involves a series of steps. An experiment was carried out to study the effect on the yield of using three methods in the cleansing step (coded to maintain confidentiality).
The results (stored in Yield-One Way) are as follows:

a. At the 0.05 level of significance, is there evidence of a difference in the mean yield among the methods used in the cleansing steps?
b. If appropriate, determine which methods differ in mean yields.
c. At the 0.05 level of significance, is there evidence of a difference in the variation in yields among the different methods?
d. What effect does your result in (c) have on the validity of the results in (a) and (b)?

Ne New2 Standard 38 34 38 34 19 28 29 35 34 20 35 37 31 23 38 29 32 30