In metrics the most honest finding will be that your metrics will have degrees of variation. Understanding where and how those metrics occur, is the key to using your data in a forward thinking strategy. Let’s start with something simple, like toy production. We are going to track some standard variation sources.
Within Unit Encoding
This variation source occurs when you are measuring output from a single production cycle. Some places that variation is likely to occur are the width of parts, color shading, length of toy etc. Now you can choose to analyze different production cycles on the same day or alternating days, but you will always be comparing samples from the same cycle. A new production sample means a new data point.
Between Unit Encoding
These names are dead giveaways, but I digress! This implies that you are looking at samples from two different production cycles. This is different in that you would want to identify two different samples from different production cycles. The variations you are looking for will give you some clue as to whether the variations are operation influenced or process influenced.
This is the trickiest variation source. This specifically calls for you to compare your variation averages from all of your data points in a single day. So you can theoretically have both within unit variation data and between unit variations data, depending on how specific you need to get.
The key to getting the most out of your data is to understand what it’s telling you. Understanding where the variations are coming from is the first step to getting the most out of your data.
We opened last week with Process Capability and before we go full-fledged into that area, I want to pause and put some focus on capability studies.
What is a Capability Study?
To review from last week, a capability study is a way to ensure that your process is consistent over an extended period of time. For example if step 3 in your process produces 3 errors per cycle for 3 years, your process in consistent.
How Do You Find Stability?
There are a ton of tools you can use to test the stability of your process, but some of the most common tools are Time Series Plots and Control Charts. In addition to these tools there is a step by step process (of course!) to test the capability of your process, here they are.
What should know about capability studies?
As with all 6Sigma tools, the effectiveness of this tools lies more in how you understand and how you apply it. The most important things to remember are:
- Capability studies are used to measure the same parts of the process, at the same stage in the process at exactly the same time every time it is measured.
- You can use the capability study on discrete and continuous data.
- You get the best (ie most meaningful) information when you run the study on already stable and predictable data. New processes are not the best place for this tool.
- When you hear Sigma Level, they are talking about capability.
- Capability studies require you to understand:
- The limits of your customer or organization.
- The difference between short-term and long-term
data and what those differences mean to your organization or customer.
- Mean and standard deviation.
- How to assess normality of your data.
- How your organization or customer determine Sigma level.
Capability Studies can give you a great deal of insight on how your organization is running and what is making it difficult. This is one way to get a sense of the information flow and the quality of the information you can get your hands on. So let’s start off the new year with a look at what your data is telling you. Happy Hunting!
Everything we measure generates variation, especially when there are multiple hands involved. To be honest even with just one person performing the same function, there will be some variation. Variation is not the enemy, uncontrolled variation is our nemesis!
When creating a Measurement System Analysis (MSA) there are 3 characteristics that you should focus on before you try any of the bells and whistles.
Is it accurate?
You need to know how accurate your measurement system is. If you can’t correctly count the number of variations happening can you really call them variations? Your measurement system is only as good as your accuracy, so it makes sense to spend a fair amount of time ensuring that not only are you counting defects, but you are counting the correct defects. This goes back to knowing why you want to measure something. If you want to find out why your shipments are late, measuring the number of birds around your facility won’t help. So accuracy needs two things: measuring the right data and ensuring the data is being measured in a way that answers your question.
Is it precise?
We’ve talked about precision and for a refresher precision is the reduction in variation. When you have identified your improvement area in the process, you are now ready for precision. So you are going to take one process, completed by the same person, in the same order every single time. Once you have identified this, you can began to reduce the variation and create precision.
Can you reproduce it?
The thought behind automating any process is ultimately making it scaleable, that is can you repeat the success? This is what determines a successful process from a failed one. Any process is good in theory, but where you get a great process is when you find one that can be repeated with the same amount of variation no matter who does it. That’s your end goal folks.
So we’ve covered the 3 basic characteristics of a Measurement System Analysis, so have a conversation with your belt and figure out your current state and your future. Your MSA will heavily influence your future, so take this conversation seriously. If you need more help, give us a call and let us help.
Continuing on my mission to make Six Sigma something that anyone can understand, today I want to keep the statistics conversation going with the scaled data, scales of measurement and what they mean to your company. There are four scales of measurement in Six Sigma to consider: Nominal, Ordinal, Interval and Ratio.
Nominally Scaled Data
This is the most basic scale and basically tells you whether the information is different or not. This applies to your business in the sense that it tells you the baseline in a yes or no format. Think along the lines of ‘does your customer buy product x’? The answer can only be yes or no.
Ordinal Scaled Data
This data applies to data that can be arranged in a specific order but you cannot distinguish what makes the data different. If you are looking for an answer to why a defect is happening, ordinal data is not going to answer that question.
Interval Scaled Data
This is the sweet spot in terms of data analysis, in this scale the data is able to be arranged in a way that tells you why the defect is happening in specific scenarios. Think along the lines of you need to know why you make more sales on Saturdays. You can measure the sales on Saturdays, the specials you offered on Saturday and how many sales corresponded to the specials offered on Saturday.
Ratio Scale Data
This scale is the most advanced analytic method. When you use this method you have data that has an absolute value and when you get a value of 0 is shows that there is no correlation between the variable and the measurement. For example, you have 10 programmers and programmer A completes 20 lines of code, programmer B completes 15 lines of code. If programmer C actually completes) lines of code, then you can say that no code was completed on that specific day.
Knowing how to analyze data is a big tool in your Six Sigma tool bag. Now this is not an exhaustive list, but when you sit down to meet with your belt now you know what you need to ask and what the belts information should be telling you. When you are ready to get started, let us know and we can help you.
Process mapping is an excellent tool that doesn’t have to be monopolized by 6Sigma professionals. The best thing about a process map is the ability to illustrate the problem. Often times in an organization we understand that there is an issue, but we just don’t know what it is. Process mapping helps you to literally see the problem.
How does it work?
Like all things 6Sigma it can be as complicated or as simple as you would like for it to be, having said that there are a few steps that I think you should include in your mapping effort.
1. Define what you need to know.
2. Identify one process at a time and take the process from cradle to grave.
3. In the beginning, stick to linear maps and be sure to define decision points.
4. Identify if different departments/people participate in the process and define those elements.
What does it look like?
Bottom line –a process map should illustrate your steps and show your organization exactly where you are. When you know where you are, you know where to go. This is a minimum, but give us a call and we can help you with the specifics.