Flex Products is a subcontractor of General Motors,
manufacturing mechanical speedometer cables.
The basic cable design has not changed for fifteen years
and General Motors had experienced many disappointing attempts
at reducing the speedometer noise level.
Usage
data(FLEXPROD)
Arguments
source
Kenett, R. and Zacks, S. (1998)
Modern Industrial Statistics: The Design and Control of Quality and Reliability.
Duxbury Press.
Details
Problem Definition: the product under investigation is
an extruded thermoplastic speedometer casing used to cover the
mechanical speedometer cable on automobiles. Excessive
shrinkage of the casing is causing noise in the mechanical
speedometer cable assembly.
Response variable: the performance characteristic in this
problem is the post extrusion shrinkage of the casing. The percent
shrinkage is obtained by measuring approximately 600mm of casing that
has been properly conditioned $(A)$, placing that casing in a two hour
heat soak in an air circulating oven, reconditioning the sample and
measuring the length $(B)$.
Shrinkage is computed as: $Shrinkage = 100 * (A-B)/A$.
Factor Levels: Existing (1) - Changed (2)
Number of Replications: four random samples of 600mm from the
3000 feet manufactured at each experimental run.
Data Analysis: signal to noise ratios $(SN)$ are
computed for each experimental run and analyzed using main
effect plots and an ANOVA. Savings are derived from Loss
function computations.
The signal to noise formula used by Quinlan is:
$$\eta = -10 log_{10} (\frac{1}{n} \sum y^2)$$