2^3 Factorial Experiment lecture - 26

 Introduction to 2^3 Factorial Experiment

lecture - 26

The 2^3 factorial experiment is the extension of 2^2 factorial experiment to three factors named A, B, C and each factor at two levels say a0, a1, b0, b1, c0, c1. In this experiment 3 factors each at two levels are analyzed.

The 2^3 factorial experiment is represented by the following linear statistical model:

 Yijkl = μ + αj + βk + γl + (αβ)jk + (αγ)jl + (βγ)kl + (αβ)γjkl ϵijkl        i = 1, 2, ..., r    j, k,  l = 0, 1



The standard form of 2^3 factors combinations are:

1

a

b

ab

c

ac

bc

abc


Assume that the total response values are:

The response values can be arranged in a three-dimensional contingency table as:

The sums of squares of total, blocks and treatment can be computed as:


The sums of squares A, B and interaction effect can also be computed as:

ANOVA Table:


Where:


 Example: The following table gives treatment combination of 3 factors:

Replicate

a

b

c

abc

1

ab

ac

bc

1

1.9

1.6

2.1

3.8

1.3

3.2

2.8

3.2

2

3.0

2.7

3.0

4.8

2.2

4.1

3.9

4.1

3

4.0

3.8

2.1

5.9

4.2

5.2

5.1

5.0

4

1.9

1.5

2.0

3.9

1.1

3.4

3.0

3.0

Write statistical model for the above stated experiment and test the significance of factors effects and interaction effects.

Solution: The statistical model of the above experiment (2^3 Factorial Experiment ) is:

Yijkl = μ + Aj + Bk + Cl + (AB)jk +(AC)jl +(BC)kl + (ABC)jkl ϵijkli = 1, 2, 3, 4. j, k,  l = 0, 1

We setup our hypotheses as:

i.  The null and alternative hypotheses can be stated as:

H01 : Aj = 0 Vs. H11 : Aj  0

H02 : Bk = 0 Vs. H12 : Bj  0

H03 : Cl = 0 Vs. H13 : Cl  

H04 : ABjk = 0 Vs. H14 : ABjk  0

H05 : ACjl = 0 Vs. H15 : ACjl  0

H06 : BCkl = 0 Vs. H16 : BCkl  0

H07 : ABCjkl = 0 Vs. H17 : ABCjkl  0

ii. The significance level; α = 0.05

iii. The test statistic:


iv. Reject all H0's, when F = > 4.32
v. Computation: using Contrast method







ANOVA Table:

vi.                    Remarks:

The effects pf factor A, B, C and their order interaction (ABC) are significant.

Example: The data of the following table are form 2 X 2 factorial experiment. Partition the treatment sum of squares into main effects and interaction counter parts. Interpret your results:

Solution: The data look like from homogeneous experimental units. So, we are using  CRD 2^2 factorial experiment.
.i. Statement of hypotheses:
H0 : T1 = T2 = T3 = T4 Vs. H1 : T1 ≠ T2 ≠ T3 ≠ T4

H01 : αj = 0  Vs. H11 : αj≠ 0

H02 : βk = 0 VS. H12 : βk ≠ 0

H03 : (αβ)jk = 0  Vs. H13 : (αβ)jk ≠ 0
ii. The significance level; α = 0.05
iii. The test statistic: 2^2 factorial experiment with CRD
F = MST / MSE ~ F(3, 16)

F1 = MSA / MSE ~ F (1, 16)

F2 = MSB / MSE ~ F (1, 16)

F3 = MS(AB) / MSE ~ F (1, 16)
iv. Reject H0, if F => 3.24
     Reject H0i, if F = > 4.49 i = 1, 2, 3
v.  Computation:






ANOVA Table:


vi.                    Remarks:

H0 is significant.and H03 are significant.


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