Variance

Variance of

about mean

meanfromtarget

NOTE:

Secondmomentabout mean

Secondmomentabout target

•

Can be usedto separatethe amountof the "problem"due to:

- Deviationof meanfromtarget

(miscentered/mis-targeted)

from

-

Deviationof parts frommean

("Processvariability")

S2=∑(x-T)2
TN

ST

2

=S

2

+(x

-T)2

(x

-T)2

+

S

2

σ2=S2=∑(x-x

)2

N
Population

•

Fitnessfor use— Juran

•

Conformanceto requirements— Crosby

•

Meetingexpectationsof customers— Feigenbaum

•

Minimizationof the lossimpartedto societyby a product due to deviationsof

the product'sfunctional characteristicsfromdesiredtargetvalues— Taguchi

•

Conformancetotargetand reductionof variability — Luftig

Distibuitionof colorconcentration(fromASAHI, 4/17/79)

An example: SonyTVcase