Six Sigma Overview
Six Sigma is a generally accepted methodology that focuses on civilizing an organization’s operational performance, business practices and systems by identifying and avoiding defects and inconsistencies in processes
If we have a procedure operating at 3sigma then we are allowing 66801.7 errors per million opportunities. Achieving six sigma funds that the process is delivering only 3.4 defects per million opportunities, in other words they are functioning nearly perfectly
The selection of six sigma project should be aligned with strategic business ambitions which could be any of the following
· Cost Reduction
· profitability improvement
· Increased customer satisfaction
· Improvement in product , service quality
· Reduction in lead time of product
· Improved employee performance
In this white paper, DMAIC, the most roughly used six sigma methodology will be explained through the case study of civilizing Test Productivity. By humanizing test productivity we can guarantee Cost Reduction and Customer Satisfaction.
Six Sigma Process
DMAIC is used when a manufactured goods or process already exists but is not meeting requirement or performance expectations. The DMAIC methodology is comprised of five phases:
- Define the project goals and customer requirements
- Measure the process to determine the current performance
- Analyze and determine the root causes of the defects
- Improve the method by eliminating defect root causes
- Control future method performance
Case Study -Implementation of DMAIC
Definition– This step recognizes the customer requirements and the Critical to Quality (CTQ) potentials of the customer. This CTQ concept in six sigma allows to focuses on quality from the perspective of the customer.
In our example, the CTQ is Test Productivity. The key components of test productivity are shown below in fig 1
Though to understand the component most critical to the customer, the Voice of the Customer (VOC) requirements to be captured.
The VOC can be obtained in several ways –
- Focus Groups
- Surveys and Organizational Metrics
- CTQ Drilldown
- Quality Function Deployment (QFD)
- Involves rating customer requirement, to find out the most critical requirement.
In this example the customer provides QFD rating as shown in table 1– Here the customer gives significance ratings to each of these requirements. Higher rating resources higher importance.
Based on the QFD rating, we now know that the CTQ to get better is Execution Productivity
Measure – In this stage, we measure the capability of the current process to meet the customer requirements. This phase consists of the following steps
- Set Performance Standard
- Prepare data collection plan
- Collect data
- Measure Process Capability
Set Performance Standards
Here we found specification limits, our target for improvement in the CTQ or Y, setting an aim that is aggressive but attainable
Now, that we have set our target for development as 40, the next step is design a data collection plan and collect data
Data Collection Plan
Sampling – When data to be composed is huge, resulting in prohibitive costs .we will go in for Sampling. This can be broadly classified as
- Random sampling – Every datapoint in the populace has a equal chance of getting selected
- Stratified Random Sampling – The population is divided into wide groups and then randomly sampled within
- Systematic Sampling – The total population N is sub-classified into a sample population n and data collection
In this example, execution productivity of testers in 2007 is the total population N, the execution of testers for the July Release is the sample n
Now that we have the information we move onto measure the current process capability
Measure Process Capability – Here, we calculate the current process capability. This involves the following steps
- Verify the process is normal
- Determine the process capability in terms of standard deviation
These steps are performed using Minitab, a standard statistical surround used in six sigma projects
The attitude behind Six Sigma is to lessen variation in the business and take customer-focused and data determined decisions. Initially clinch as a manufacturing discipline, Six Sigma methodology is now functional to every surface of business, from production to human resources to arrange entry to technical support. Six Sigma methodologies can be worn for any activity that is anxious with cost, timeliness and quality. Research recommend typical benefits will exceed costs within 6 to 12 months from beginning of a Six Sigma program for software development, and the on-going revisit will be very substantial — often a 15-25% reduction in software development costs in year two, with enduring reductions thereafter.
Some of the areas in testing where six sigma can be used are civilizing test effectiveness, increasing test coverage etc.