Six Sigma - Introduction

Six sigma, as is widely known, is 3.4 defects in a million products / operations / opportunities. Sigma levels can at 2, 3, 4, 5 and 6. The corresponding percentages of sigma levels, defects per million and their corresponding percentages are shown in the table.

Six Sigma has two views: one as a Measure of performance, and second as a methodology / philosophy to bring in process improvements. The first view of Six Sigma as a measure of performance is the myopic view, where current process performance is scaled to match sigma-levels (e.g. this statement - “The current process is operating at 4 sigma level”). The broader view of seeing six sigma is as a Methodology. It doesn’t mean you have to map it to sigma levels. Six Sigma methodology can be used to measure current process performance and scale up to a targeted level of “acceptable process performance” (USL/LSL). Not all companies would like to go for sigma levels of maturity (may not be aligned to business goals). Six Sigma is a philosophy that changes the way of thinking within a company. It brings in process awareness, helps in understanding problems at process levels, and inculcates process thinking at organization level.

Six Sigma is strictly a business improvement methodology. It uses the concept of normal curve (also known as Gaussian curve / Bell curve) + Shewart’s control charts + Ishikawa diagrams (fish bone diagrams) + other management and statistical tools & techniques to bring down defects.

Bill Smith is the father of Six Sigma. This term was coined by him.

Six Sigma methodology is to be applied where there is a likelihood of error occurrence (i.e., not on final inspection, but at intermediate stages before the final delivery of the product). Thru six sigma, we try to resolve problems permanently so that they never recur. This makes it possible for us to focus our time on planning futuristic projects / foreward thinking instead of being in an endless loop of working and reworking.

Usually, results of six sigma implementation are guaged by the financial gains, which are direct indicators of effectiveness of the program. However, sometimes improvement directly in terms of financial gains may not be possible to show. Alternate key performance indicators (KPI) are monitored to evaluate the effectiveness of a six sigma program.

Companies ARE NOT CERTIFIED SIX SIGMA. A company's processes are of six sigma level, not the company itself. Companies focus on critical processes and then take it upto six sigma level.