I found that this website gives a good guide https://controls.engin.umich.edu/wiki/index.php/Design_of_experiments_via_taguchi_methods:_orthogonal_arrays
here is my example
So let’s have a look at this example,
We are testing a website for a car dealership
· they sell 3 different types of vehicles
o Hatch back
o Sedan
o Ute
· Each vehicle type comes in 3 different Interior packages
o Economy
o Sports
o Luxury
· Each vehicle type comes in 3 different Wheel packages
o Steel wheels
o Sports alloys
o Luxury 18’ inch wheels
The company wants to know be assure that each combination of car type and package can be ordered from there website
Looking at the follow table we can easily workout which Orthogonal array is required for the example on the previous page In this case we need L9 as we have 3 parameters with 3 levels the next step is to replace the values in the table with the value of the Parameters and our levels Below is the array before replacing the values
Test
P1
P2
P3
P4
1
1
1
1
1
2
1
2
2
2
3
1
3
3
3
4
2
1
2
3
5
2
2
3
1
6
2
3
1
2
7
3
1
3
2
8
3
2
1
3
9
3
3
2
1
Now all we have to do is replace the values, as we only have 3 parameters the final column is removed
Test
Vehicle type
Interior package
Wheel Package
1
Hatch back
Economy
Steel wheels
2
Hatch back
Sports
Sports alloys
3
Hatch back
Luxury
Luxury 18s
4
Sedan
Economy
Sports alloys
5
Sedan
Sports
Luxury 18s
6
Sedan
Luxury
Steel wheels
7
Ute
Economy
Luxury 18s
8
Ute
Sports
Steel wheels
9
Ute
Luxury
Sports alloys
Note this doesn’t cover every possible combination but does cover all different pairs