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Robert Butler replied to the topic Statistical Power for Two Samples TTest in the forum Tools & Templates 4 months, 1 week ago
Something doesn’t seem right. I would like to check the calculation. Could you post your total sample size and the values of the two averages?

Robert Butler replied to the topic How Do You Conduct a Baseline Performance Analysis? in the forum New to Lean Six Sigma 4 months, 2 weeks ago
Let’s see if we can’t get you off of dead center.
You said the following:
Given a set of data, how do you conduct a baseline performance analysis? Is this the same as a capability analysis?
And, when looking at a set of data, how can you tell where the process changed?
My assignment asks me to complete a baseline performance analysis and “if t…[Read more]

Robert Butler replied to the topic Happy Birthday Mike Cyger in the forum General 4 months, 3 weeks ago
I’ve been away from any computer contact for the last 10 days, however, Happy belated birthday Mike… 19 July…hmmm interesting day that….
Circus Maximus catches fire – 64
15yearold Lady Jane Grey deposed as England’s Queen after 9 days 1553
Astronomer Johannes Kepler has an epiphany and records his first thoughts of what is to become…[Read more]

Robert Butler replied to the topic Trying to Understand Null Hypothesis Question in the forum General 5 months ago
I guess what I find most disturbing about the statement “these are actual questions from the exams” is the very real possibility of failing someone because they DID know the material and, conversely, passing someone who was ignorant of the correct answer.

Robert Butler replied to the topic Trying to Understand Null Hypothesis Question in the forum General 5 months ago
In this instance the question does not make sense. The usual way one describes Type I and Type II error is as follows:
Type I error is the risk of rejecting something when it is true.
Type II error is the risk of accepting something when it is false.
So the risk of rejecting something when it is false doesn’t meet the definitions of either…[Read more]

Robert Butler replied to the topic Need Help with Ppk Calculation in the forum Tools & Templates 5 months ago
It looks to me like they’ve screwed up again. Answer C is the estimate of the standard deviation (24/6). Your calculations are correct.

Chuck White and Robert Butler are now friends 5 months ago

Robert Butler replied to the topic Need Help with Factorial Design LSSBB Practice Question in the forum Tools & Templates 5 months ago
I’m sure they do. Here’s the issue
1. What exactly is a 32 factorial design? I’m not aware of any reference that expresses design nomenclature in this manner.
The usual practice is to say say things such as the following:
1. I have a two level design with 3 factors
2. I have a full 2 level factorial design for 5 variables for a total run of…[Read more] 
Robert Butler replied to the topic Need Help with Factorial Design LSSBB Practice Question in the forum Tools & Templates 5 months ago
I would say C,D,E and I think C is a typo – my guess is that they meant to have 3*2 = 6 experiments.
Actually, there is another possibility – but if it is the case then the problem is poorly presented and C still remains a typo. Since they do claim it is a factorial design one could take a saturated 3 variable in 4 experiments design and augment…[Read more]

Robert Butler and Katie Barry are now friends 5 months ago

Robert Butler replied to the topic Probability of an Average for a Group Based on Individual Value Distribution in the forum Tools & Templates 5 months, 1 week ago
I think you will need to provide some additional details.
1. In your first post you are talking about weight and in your second post you are talking about height – which is it?
2. In your first post you will need to clarify what you mean by “I have a normal distribution for a coating weight per part of 1 gram/m2 and a standard deviation of…[Read more] 
Robert Butler replied to the topic Gage R&R with One Part, One Operator, 10 Tries in the forum Tools & Templates 5 months, 1 week ago
No, it’s not a case of the less you have of repeated measures the less precision you have on the value of the standard deviation of the GRR rather it is a matter of the less you have of repeated measures the better the precision of your estimate of the true value of the standard deviation of the GRR. As I said – repeated measures variation will…[Read more]

Robert Butler replied to the topic Gage R&R with One Part, One Operator, 10 Tries in the forum Tools & Templates 5 months, 1 week ago
In addition to what @cseider said you also do not have independent measurements – you have repeated measures on a single item which means your estimates of variation are going to be much less than the real variation you can expect in your process.

Robert Butler replied to the topic How to Analyze Nonnormal Data and Indicate the Capability of the Process? in the forum Tools & Templates 5 months, 2 weeks ago
I’m not trying to be funny at your expense but if you really have a process like this then then next Nobel Prize in Physics will be yours on demand because you have found a process that exhibits zero variation which means you have invalidated the second law of thermodynamics – something that heretofore was deemed physically…[Read more]

Robert Butler replied to the topic Need Help Analyzing NonNormal Data in the forum Tools & Templates 5 months, 2 weeks ago
I would recommend you reexamine your data. The IMR plot gives a visual impression of three distinct shifts downward in your data. The first cut point occurs at about data point 44, and the second at about data point 83. It also gives the impression the process is drifting back toward the target around data point 93. In short, the plot would…[Read more]

Robert Butler replied to the topic Why Are Linear Plots Mostly Used in Regression? in the forum Tools & Templates 5 months, 3 weeks ago
I’m not trying to be sarcastic but who is making the claim that linear plots are mostly used in [an examination?] of a linear regression?
There are any number of reasons why an analysis might result in employing simple linear plots. For example:
1. Your plan for analysis involves running a two level factorial design. – In this case, by…[Read more] 
Robert Butler replied to the topic Need Help Analyzing Variance with Minitab in the forum Tools & Templates 5 months, 4 weeks ago
I see I spoke too soon. What I said above still applies with respect to the graphical presentation and sampling plan you should use when repeating your test but since you provided the actual data there are a couple of other things to consider.
Again, if we pretend the sequential measures within a given operator are independent (they’re not)…[Read more]

Robert Butler replied to the topic Need Help Analyzing Variance with Minitab in the forum Tools & Templates 5 months, 4 weeks ago
I don’t know Minitab but I do know they have boxplots graphics which I would recommend you use. You would have sidebyside boxplots of the two shifts. What you will want to do is to make boxplots which also shows the raw data that way you will not only have the boxplot with its summary statistics but you will be able to see visually just how…[Read more]

Robert Butler replied to the topic Need Help Analyzing Variance with Minitab in the forum Tools & Templates 6 months ago
Just a visual impression of your data says you have a statistically significant difference in mean scoop size between first and second shift. If we check it formally and pretend the measures within each team member can be treated as independent measures then what you have is 1.22 vs 1.88 (which, given the limit on significant digits reduces to…[Read more]

Robert Butler replied to the topic What Was Your Career Path Into Process Improvement? in the forum General 6 months ago
Wellll…not counting the mandatory military service I don’t think there’s been any time in my career when I wasn’t involved in process improvement. I started off as a physicist working in advanced optics – the work was a combination of R&D and improving existing systems/processes. One of the groups I worked with had an assigned statistician. I…[Read more]
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