Page 318 - Six Sigma Demystified

298 Six SigMa DemystifieD

Interpretation

Level loading ensures that goods produced at each step are used immediately
by the next step, ensuring a constant flow of items (or service) through the
value stream. If a temporary increase in orders is received, the pace remains the
same, but resources are moved to meet demand.

Linearity Analysis

Linearity analysis provides an indication of whether the bias error associated
with a measurement system is constant throughout the operating range of the
equipment. In other words, is the measurement system equally accurate for
large measurements as for small?

When to Use

Measure Stage
• To evaluate the accuracy of a measurement system throughout the range
of measurements required for the process

Methodology

The Automotive Industry Action Group method (AIAG, 1995) of calculating
linearity is as follows: Choose two or more parts (product or service types)
throughout the operating range of the gauge. Measure the pertinent character-
istic using high-accuracy gauges, such as those used in layout inspections, to
obtain a reference value. Using the gauge to be studied, have one or more pro-

cess personnel measure the characteristic multiple times. Calculate the average
of these measurements for each part. Calculate the bias for each part as the
difference between the gauge average and the reference value. Using a scatter
diagram, plot the reference value (x axis) versus the bias (y axis).

Linearity

Minitab

Data input: Enter columns for part/item designator, reference value, and mea-
sured value.