ETM 421 Morehead State University General 2k Factorial Designs Question

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RU1996

Mathematics

etm 421

Morehead State University

ETM

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Assignment Objectives: 1. Know how to compute main effects and interactions for general 2 factorial designs. 2. Apply the ANOVA techniques to general 2 factorial designs. 3. Learn how to check model assumptions such as normality, constant variance, and independence in 2 factorial designs. Problems: 1. An experiment was performed to improve the yield of a chemical process. Four factors were selected, and two replicates of a completely randomized experiment were run. The results are shown in the following table: k k k Treatment Replicate Replicate Treatment Replicate Replicate Combination I II Combination I II (1) 91 94 d 99 96 a 75 79 ad 73 77 b 82 86 bd 88 84 ab 84 81 abd 86 87 c 78 79 cd 100 91 ac 82 81 acd 80 76 bc 89 83 bcd 88 85 abc 74 71 abcd 81 81 a. Prepare an analysis of variance table, and determine which factors are important in explaining yield. b. Plot the residuals versus the predicted yield plot and the normality plot of residuals. Does the residual analysis appear satisfactory? 2. An engineer is interested in the effects of cutting speed (A), tool geometry (B), and cutting angle (C) on the life (in hours) of a machine tool. Two levels of each factor are chosen, and three replicates of a 23 factorial design are run. The results are as follows: Treatment Combination A B C - - - + - - Replicate I II III (1) 22 31 25 - a 32 43 29 + - b 35 34 50 + + - ab 55 47 46 - - + c 44 45 38 + - + ac 40 37 36 - + + bc 60 50 54 + + + abc 39 41 47 a. Prepare an analysis of variance table, and determine which factors are important in explaining the life of the machine tool. b. Plot the residuals versus the predicted tool life plot and the normality plot of residuals. Does the residual analysis appear satisfactory?
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Solutions
Question 2

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BC

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Total sum of replication
(1) = 78
a = 104
b = 119
ab =148
c = 127
ac =113
bc =164
abc =127

Average effect of: factor A
𝐴 = 𝑦̅𝐴+ − 𝑦̅𝐴− =

(𝑎+𝑎𝑏+𝑎𝑐+𝑎𝑏𝑐)
4𝑛

-

(1)+𝑏+𝑐+𝑏𝑐
4𝑛

= 1/4n (a + ab + ac + abc – (1) – b – c – bc)
=

1
4×3

(104 + 148 + 113 + 127 – 78 – 119 -127 – 164)

=1/12 (4) = 0.3333
Average effect of: factor B
𝐵 = 𝑦̅𝐵+ − 𝑦̅𝐵− =
=

1

(𝑏+𝑎𝑏+𝑏𝑐+𝑎𝑏𝑐)
4𝑛

-

(1)+𝑎+ 𝑐+𝑎𝑐
4𝑛

((119 +148 + 164 + 127) – ( 78 +104 + 127 + 113))

4×3

= 1/12 (136) = 11.3333

Average effect of: factor C.
𝐶 = 𝑦̅𝐶 + − 𝑦̅𝐶 − =

(𝑐+𝑎𝑐+𝑏𝑐+𝑎𝑏𝑐)
4𝑛

-

(1)+𝑎+ 𝑏+𝑎𝑏
4𝑛

1

= 4×3 (( 127 + 113 + 164 + 127 ) – (78 + 104 + 119 + 148 ))
= 1/12 (82) = 6.8333
Two- factor interaction effect between:
Factor A and B

AB =
=

(𝑎𝑏+𝑎𝑏𝑐−𝑎−𝑎𝑐)
4𝑛

(𝑏+𝑏𝑐−(1)−𝑐)

-

(148+127−104−113)

4𝑛
(119+164−78−127)

-

4∗3

4∗3

= 1/12 ((148+127+78+127) – (104 + 113 +119+164))
= 1/12 (-20)
= -1.6667
Factor A and C
AC =
=

(𝑎𝑐+𝑎𝑏𝑐−𝑎−𝑎𝑏)
4𝑛

(𝑐+𝑏𝑐−(1)−𝑏)

-

(113+127−104−148)

4𝑛
(127+164−78−119)

-

4∗3

4∗3

= 1/12 ((113+127+78+119) – (104+ 148 +127+164))
= 1/12 (-106)
= -8.3333
Factor B and C
BC =
=

(𝑏𝑐+𝑎𝑏𝑐−𝑏−𝑎𝑏)
4𝑛

(𝑐+𝑎𝑐−(1)−𝑎)

-

(164+127−119−148)
4∗3

4𝑛
(127+113−78−104)

-

4∗3

=1/12 ((164+127+78+104) – (119+148+127+113)
=1/12 (-34)
= -2.8333
Three factor interaction between:
Factors A, B and C
BC =
=

(𝑎𝑏𝑐−𝑏𝑐)−(𝑎𝑐−𝑐)
4𝑛

-

(127−164)−(113−127)
4∗3

(𝑎𝑏−𝑏)−(𝑎−(1)

-

4𝑛
(148−119)−(104−78)
4∗3

=1/12 ((127+104+119+127) – (148+113+164+78))
= 1/12 (-26)

= -2.1667
Let Г be the sum of the numerator for every factor.
Then,
The sum of squares associated with every factor is given by;
Г2

𝑆𝑆𝑖 = 8𝑛𝑖
Г2

𝐴
𝑆𝑆𝐴 = 8∗3

42

=

8∗3

= 0.6667

Г2

𝐵
𝑆𝑆𝐵 = 8∗3

=...

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