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An engineer is interested in the effect of cutting speed ( A ), metal hardness ( B ), and cutting angle ( C ) on the life of a cutting tool. Two levels of each factor are chosen, and two replicates of...

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An engineer is interested in the effect of cutting speed (A), metal hardness (B), and cutting angle (C) on the life of a cutting tool. Two levels of each factor are chosen, and two replicates of a 23factorial design are run. The tool life data (in hours) are shown in the following table:

 

Replicate

Treatment  Combination

I

II

(1)

221

311

a

325

435

b

354

348

ab

552

472

c

440

453

ac

406

377

bc

605

500

abc

392

419

replicate 1 only. Suppose that a center point with four replicates is added to these eight factorial runs and the responses are 425, 400, 437, and 418.

(a) Estimate the facter effects.

(b) Test for lack of fit using α = 0.05

(c) Test for main effects and interactions using α = 0.05.

(d) Analyze residuals and draw conclusions.

Answered Same Day Dec 24, 2021

Solution

David answered on Dec 24 2021
120 Votes
(a) Estimate the factor effects. Which effects appear to be large?
From the normal probability plot of effects below, factors B, C, and the AC interaction appear to be significant.


(b) Use the analysis of variance to confirm your conclusions for part (a).
The analysis of variance confirms the significance of factors B, C, and the AC interaction.

Design Expert Output
Response: Life in hours
ANOVA for Selected Factorial Model
Analysis of variance table [Partial sum of squares]
Sum of Mean F
Source Squares DF Square Value Prob > F
Model 1612.67 7 230.38 7.64 0.0004 significant
A 0.67 1 0.67 0.022 0.8837
B 770.67 1 770.67 25.55 0.0001
C 280.17 1 280.17 9.29 0.0077
AB 16.67 1 16.67 0.55 0.4681
AC 468.17 1 468.17 15.52 0.0012
BC 48.17 1 48.17 1.60 0.2245
ABC 28.17 1 28.17 0.93 0.3483
Pure E
or 482.67 16 30.17
Cor Total 2095.33 23
The Model F-value of 7.64 implies the model is significant. There is only
a 0.04% chance that a "Model F-Value" this large could occur due to noise.
The reduced model...
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