Pizza Delivery Example

Imagine there are two companies delivering pizzas in a city. Their average delivery times (in minutes) are seen in the table. Say, the upper specification limit is 30. That is the pizza has to be delivered within 30 minutes no matter where the client resides (within the city). (This limit is self-defined by the pizza outlets)

The Average for both the outlets is 20. But, as can be perceived by looking at the values, Outlet A seems to be more consistent, and shows less variability in cooking & delivering pizzas compared to Outlet B. Mean therefore is not a proper measure for comparing variations. A better way is thru standard deviation.

Instead of comparing process variability thru Mean, compare the sigma levels, which give a better insight into the process variability.

For Outlet B to better its process performance, it can target these: 1. Mean. 2. Standard Deviation 3. Sigma Level. Note that the specification limits cannot be changed as they are derived from customer expectations. By focusing on internal processes that are responsible for delays (such as cooking time, time lapse in dished out pizza and its pick up for delivery, etc.), Outlet B can improve on variability in delivery time.

Sigma Level = Diff bet'n mean & spec limit / Sigma

Note: In this example, the Simga Level we get is Zlt. To get Zst, add 1.5. So, as per Zst, the process of outlet A is at (7.91+1.5), and that of outlet B is (1.41+1.5).

Variability and Bell-shaped Curves

Every human activity has variability. Natural patterns of data of any process are bell-shaped curves. Most of the human processes follow a bell shaped curve. Take for example, the internet connectivity speed. Even though the connectivity speed may be 64kpbs, it is not at that speed at every point of time. It keeps on varying. At some time it may be overshoot the specified speed, and at others, remains below that. On an average, however, the connectivity is 64kbps.

Mean is the area around which most of the data points tend to cluster. Going away from the mean on either sides of the curve, values the clustering gradually come down.

Six Sigma - Green & Black Belts

Green & Black Belts: Green belts can handle most of the common situations, while black belts can address even the complex situations.

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.

Customer Satisfaction Index

Customer satisfaction has to be driven by the solution providers - not by the client. Customer satisfaction can be better tracked thru a web-based interface so that frequent exchange of emails can be avoided. In over 90% of the cases client is non committal on the feedback. So, moot up the issue while on a call discussing on technical issues. Fill up the feedback yourself in consultation with client, and send a copy to the client; baseline the data.