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A research team wished to specify a manufacturing process so that Y, the area in

ID: 3251520 • Letter: A

Question

A research team wished to specify a manufacturing process so that Y, the area in a product affected by surface flaws was as small as possible. They had four levels of concentration of a chemical used to wash the product before the final manufacturing step and wanted to determine whether different concentration levels caused a change in E(Y). They ran a balanced one-way layout with 6 observations at each concentration with level 1 set at 5%, level 2 set at 10%, level 3 set at 15%, and level 4 set at 20%. They observed that y, =21.5, y_2 = 11.2, y_3 = 18.8, and y_4 = 39.3, where y_i. was the average of the observations taken on the ith level. They also observed that s_1^2 = 81.9, s_2^2 = 92.2, s_3^2 = 71.8, and s_4^2 = 101.9, where s_1^2 was the unbiased estimate of the variance for the observations taken at the ith concentraton. The four parts of this problem are worth a total of 80 points. a. Complete the analysis of variance table for these results; that is, be sure to specify the degrees of freedom, sum of squares, mean square, and F-test. Use significance levels set to 0.10, 0.05, and 0.01.

Explanation / Answer

Answer:

Group

Mean

SD

n

Total

SSGroups

SSError

1

21.5

9.049862

6

129

8.64

409.5

2

11.2

9.602083

6

67.2

793.5

461

3

18.8

8.473488

6

112.8

91.26

359

4

39.3

10.09455

6

235.8

1653.36

509.5

ANOVA

Source

df

SS

MS

F

P-value

Groups

3

2546.76

848.92

9.763312

0.000356

Error

20

1739

86.95

Total

23

4285.76

H_0: mu_1 = mu_2= mu_3 = mu_4

H1: At least one pair of population means are different

Calculated F=9.76, P=0.0004 which is < 0.01 level.

Ho is rejected at all the 0.10, 0.05 and 0.01 levels.

Group

Mean

SD

n

Total

SSGroups

SSError

1

21.5

9.049862

6

129

8.64

409.5

2

11.2

9.602083

6

67.2

793.5

461

3

18.8

8.473488

6

112.8

91.26

359

4

39.3

10.09455

6

235.8

1653.36

509.5

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