EEM332

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EEM332

• Design of Experiments

En. Mohd Nazri Mahmud MPhil (Cambridge, UK) BEng (Essex, UK) nazriee_at_eng.usm.my Room 2.14 Ext. 6059
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Agenda
ANOVA with Excel and Minitab exercises
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Example 3-1page62
Graphical examination of the data using scatter
plots In Excel choose XY scatter plot In Minitab
, choose gtGraphgtPlotgtSpecify X and Y variable
The scatter diagram indicates increasing etch
rate with power
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Example 3-1page62
Graphical examination of the data using
boxplots In Minitab , choose gtGraphgtBoxplots
The boxplot indicates increasing etch rate with
power
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Example 3-1page62
Graphical examination of the data using
Regression Model (page 86) useful to see the
response at intermediate factor levels Linear
Model In Excel gtInsertgtChartgtXYScatter and add
trendline and show equations
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Example 3-1page62
Graphical examination of the data using
Regression Model useful to see the Response and
intermediate factors Quadratic Model choose
Polynomial order 2
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Example 3-1page62
Graphical examination of the data using
Regression Model In Minitab , choose
gtStatgtRegression
Regression Analysis Etch Rate versus RF
Power The regression equation is Etch Rate
138 2.53 RF Power Predictor Coef SE
Coef T P Constant 137.62
41.21 3.34 0.004 RF Power
2.5270 0.2154 11.73 0.000 S 21.54
R-Sq 88.4 R-Sq(adj) 87.8
The boxplot indicates increasing etch rate with
power
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Example 3-1page62
ANOVA In Minitab , choose gtStatgtANOVAgtOne-way Can
also tick Boxplot and Boxplot to select
One-way ANOVA Etch Rate versus RF
Power Analysis of Variance for Etch Rat Source
DF SS MS F P RF
Power 3 66871 22290 66.80
0.000 Error 16 5339
334 Total 19 72210

• gt Between treatment mean square gtgt
  within-treatment(error) mean square
• F-value 66.8 gt F 0.05,3,16 (3.24)
• P-value is very small

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Analysis of variance Exercises using Minitab
Question 1
The tensile strength of portland cement is being
studied. Four different mixing techniques can be
used economically. A completely randomised
experiment was conducted and the following data
collected.
Mixing Technique Tensile Strength Tensile Strength Tensile Strength Tensile Strength
1 3129 3000 2865 2890
2 3200 3300 2975 3150
3 2800 2900 2985 3050
4 2600 2700 2600 2765
Perform ANOVA using Minitab to test the
hypotheses that mixing techniques affect the
tensile strength
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Analysis of variance - Exercise
Q 2
A manufacturer of television sets is interested
in the effect of tube conductivity of four
different types of coating for color picture
tubes. The following conductivity data are
obtained.
Coating Type Conductivity Conductivity Conductivity Conductivity
1 143 141 150 146
2 152 149 137 143
3 134 136 132 127
4 129 127 132 129
Perform ANOVA using Minitab to test the
hypotheses that coating types affect the
conductivity.
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Analysis of variance - Exercises
Q 3
Four different designs for a digital circuits are
being studied in order to compare the amount of
noise present. The following data have been
obtained.
Circuit designs Noise observed Noise observed Noise observed Noise observed Noise observed
1 19 20 19 30 8
2 80 61 73 56 80
3 47 26 25 35 50
4 95 46 83 78 97
Perform ANOVA using Minitab to test the
hypotheses whether the noise are the same for all
the four designs or not.