Page 319 - Six Sigma Demystified

Part 3 S i x S i g m a To o l S 299

Menu: Stat\Quality Tools\Gauge Study\Gauge Linearity and Bias Study
Results: Obtain slope from plot; report as percent linearity.

Excel

Using Green Belt XL Add-On
Data input: Enter columns for part/item designator, reference value, and mea-
sured value; calculate bias for each item.

Menu: New Chart\ Scatter Diagram
Data range: Select column of reference values as x axis (first column in data
range); select column of bias as y axis (second column in data range)
Results: Obtain slope from plot; report as percent linearity.

Interpretation

Use the coefficient of determination R to determine if the linear fit is ade-
2
quate. (Usually, a number such as 70 percent or higher provides sufficient lin-
earity.) If the fit is linear, then the percent linearity is the absolute value of the
slope of the regression line, reported as a percentage.

%Linearity = | slope | × 100%

Matrix Diagrams

A matrix diagram is used to show the relationship between the various items in
two or more groups. Matrix diagrams are tabular in format, where each cell
contains a numerical score that indicates the strength of the perceived relation-
ship between the row and its intersecting column.

When to Use

Define Stage
• To select projects aligned with the company’s goals and objectives
• To understand how customer requirements are aligned with process
metrics