INTRODUCTION TO SOFTWARE DESIGN FOR SIX SIGMA (DFSS) - Software Design for Six-Sigma: A Roadmap for Excellence - page 171

CHAPTER 8

INTRODUCTION TO SOFTWARE
DESIGN FOR SIX SIGMA (DFSS) 1

8.1 INTRODUCTION

The objective of this chapter is to introduce the software Design for Six Sigma (DFSS)
process and theory as well as to lay the foundations for the subsequent chapters
of this topic. DFSS combines design analysis (e.g., requirements cascading) with
design synthesis (e.g., process engineering) within the framework of the deploying
company's software (product) development systems. Emphasis is placed on Critical-
To-Satisfaction (CTS) requirements (a.k.a Big Y's), identification, optimization, and
verification using the transfer function and scorecard vehicles. A transfer function
in its simplest form is a mathematical relationship between the CTSs and/or their
cascaded functional requirements (FRs) and the critical influential factors (called the
X's). Scorecards help predict risks to the achievement of CTSs or FRs by monitoring
and recording their mean shifts and variability performance.
DFSS is a disciplined and rigorous approach to software, process, and product
design by ensuring that new designs meet customer requirements at launch. It is a
design approach that ensures complete understanding of process steps, capabilities,
and performance measurements by using scorecards, transfer functions, and tollgate

1 The word “Sigma” refers to the Greek letter, σ , that has been used by statisticians to measure variability.
As the numerical levels of Sigma or ( σ ) increase, the number of defects in a process falls exponentially.
Six Sigma design is the ultimate goal since it means if the same task performed one million times,
there will be only 3.4 defects assuming normality. The DMAIC Six Sigma approach was introduced in
Chapter 7.