Question

One Way ANOVA (Analysis of Variance)

A manufacturer of steel wants to test the effect of the method of manufacture on the tensile strength of a particular type of steel. Four different methods have been tested and the data shown in Table 1. (Use Minitab)

1. Develop the ANOVA table and test the hypothesis that methods affect the strength of the cement. Use a = 0.05
2. Use the Tukey’s method with a =0.05 to make comparisons between pairs of means.
3. Construct a normal probability plot of the residuals. What conclusion would you draw about the validity of the normality assumption?
4. Prepare a scatter plot of the results to aid the interpretation of the results of this experiment
5. Find a 95 percent confidence interval on the mean tensile strength of each method. Also find a 95 percent confidence interval on the difference in means for techniques 1 and 3. Does this aid in interpreting the results of the experiment?

                

                    Table 1

                                         Method                      Tensile Strength

                                              1                 6.5       7.6       7.5        6.0

                                              2                 9.8       9.7       8.6        8.9

                                              3                 7.7       6.2       6.9        7.0

4.              9.0       8.8       8.5        9.5

Answer 1

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Answer:

C)

as normal probability plot of residual is approximately straight line we can say assumption is valid in this case

D)