Six Sigma methodologies use statistical tools used to transform raw data into information. Based on the results, further actions are taken. Statistical tools and related aspects of Six Sigma methodology comprises about half of Six Sigma. In addition, Six Sigma places a lot of emphasis on graphical interpretation of data collected during the course of measurements.
The importance of statistical methods emanate from the fact that many hypotheses can be disproved with sufficient statistical data. The significance of statistical methods in Six Sigma increases with any increase in sample sizes. The statistical methods quantitatively facilitate evaluation of the performance of any process. The purpose of this being to tackle the cost of poor quality (COPQ) first, Six Sigma has a broader scope than the traditional cost effectiveness model.
Some Important Statistical Methods In Six Sigma
Variations in processes are measured in terms of deviation from the mean and data falling within the acceptable statistical limits. Graphical representation of this data helps companies to visualize things with greater accuracy. Let us examine a few of the most commonly used Six Sigma statistical methods.
Control Chart
The deviations within the acceptable limits (upper & lower) are due to common causes. Anything falling beyond the limits is attributable to some specific cause. For example, take the case of writing your name ten times. Although there are similarities, you probably won't be able to find any two signatures being exactly the same. The reason is an inherent variation that produces reasonable results within limits and is termed as ?common cause?. Special causes are those due to forced errors. A control chart has a mathematical mean line in the center and two limit lines. The third component of the Six Sigma control chart is the performance data, which is plotted over time.
You can seek special causes and track common ones through control charts by looking for:
?One set of data falling beyond the acceptable limits (special cause)
?Greater than 6 data sets climbing or declining steadily within limits
?Eight or more subsequent data sets falling on one side of the mean
?Data falling alternately across the mean line
Interpretation emphasizes seeking out the special cause that brings stability to process variation. The real fun here lies in removing the common cause and induced variations also.
Brainstorming & Affinity Group Tool
Brainstorming generates and polishes creative ideas based on the principle that two heads are better than one. An affinity diagram is used to organize & develop brainstorming by fine tuning initial and raw thoughts and removing uncertainties. The advantage of this is that it obviously stimulates for generation of more ideas. The affinity diagram was not originally intended to be a quality management tool. First devised by Kawakita Jiro, the affinity tool emphasizes the need for sorting and titling the data only at the end. A typical affinity diagram organizes the brainstormed ideas on its left panel. On the right side are ideas neatly grouped into affinity sets. Reasons for an idea belonging to a particular set are not given particular importance, but all ideas are clarified. An idea may be present in a single group if it has any resemblance to another.
If there is one thing that summarizes the importance of statistical methods in Six Sigma, it can be none better than a saying, famous in Six Sigma circles ? ?In God we trust, all the rest bring data?. Need we say more?
Implementing Six Sigma Smarter Solutions Using Statistical Methods
A telephone survey is a basic way to randomly select and carry out customer surveys. The sample generated can be generalized to an entire target population. A great example of this is if you want to carry out a survey of customers who have bought or have viewed a newly-launched product.
A standard questionnaire should be prepared and the interviewer makes phone calls to the customers and record the data on the basis of the information provided.
The data collected is very useful, but this method is expensive. Its success depends upon the accuracy of the questionnaire prepared. It will take a couple of weeks to get the information from the select group. The questions should be asked in a similar manner, the question wording should be the same and all the responses should be categorized.
Mail Surveys
Mail surveys can also provide companies with a substantial amount of data - and at a much lower cost than that on telephone surveys. However, mail surveys have a low response rate and can take quite a few months to complete. The lower the rate of response, the lower the reliability of the survey.
If you decide to do follow up with new letters and questionnaires, it will add on to the cost. A response rate of fifty percent is the lowest rate acceptable.
Focus Groups: In-Person
In the in-person focus group is a discussion carried out among 15-20 people who are lead by a moderator with a detailed discussion in the area on which information needs to be collected. The group cannot be generalized to the larger population, but a vast amount of data can be collected. Effective visual aids can be used for communication.
The discussion group can come up with the reasons for customer dissatisfaction and possible solutions to the problem. There are traveling costs of participants, charges on the location and so on to contend with. The entire process typically takes a week or two for preparation of guidelines and recruiting participants.
The downside, though, is that the participants can be used again at a later date.
Focus Groups: Online
Online groups are similar to in-person focus groups. The difference is that the discussion takes place on the Internet, saving companies looking to implement Six Sigma the cost of getting participants to the interview site. Online focus groups are more suited for younger age groups, as they are usually very comfortable with online chats than individuals above age 40.
This group can generate a lot of information.
One On One Interviews
If your company is implementing Six Sigma, then one-on-one interviews allow you to get detailed information that cannot be achieved from a survey - even though it cannot be generalized to the larger population. When you require information from people like CEOs, Doctors and celebrities, it is impossible to get a large group together in a meeting at the same time.
However, busy, important people like the ones above can fit interviews into their schedules. The cost involved is lower, though some costs may have to be incurred by both the interviewees and the interviewers.
Intercepts
Intercepts involve getting information from people at public locations like stores, malls or theatres. Often, the information received is of the utmost importance.
This information is generalized to a specific target group, such as women with infants who may be asked about a certain baby food. Additionally, it will be specific to that day, as well as the location.
User Testing
Six Sigma user testing involves having the individuals use the company's product while they are being observed. Alternatively, they may be made to log that data in a diary or a sheet for a period of time. This helps the company to understand if the user finds any difficulties in using the product.
The company website will also be checked in this manner. The amount of time taken to do this will vary depending on the product.
Customer Complaints
This is one way of obtaining data that will give you an idea of the problem area, but it will not necessarily be qualitative. The cost involved is low. The complaints have to be monitored and tabulated as they come in, providing a general idea of the situation.
One or a combination of these techniques can be used to listen to the customer and collect information that is necessary for any Six Sigma project to succeed.
Tony Jacowski has sinced written about articles on various topics from University, Six Sigma and Information Technology. Tony Jacowski is a quality analyst for The MBA Journal. Aveta Solution's Six Sigma Online offers online and certification classes for lean six sigm. Tony Jacowski's top article generates over 90500 views. to your Favourites.
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