## Activity

Robert Butler replied to the topic Teaching Exercises for Hypothesis Testing and DOE in the forum Training 1 week ago

For a paired frequency test you could have the students run a series of say 50 flips of a clean penny and then run a series of 50 spins of a clean penny to see if there is a significant difference in the odds of the penny coming up heads (or tails).

Robert Butler replied to the topic Question that Annoys: What Is the Main Purpose Behind Six Sigma? in the forum Welcome 1 week, 1 day ago

Well then, for heavens sake – as a favor to your mental well being – don’t ask it! ;-)

Seriously, I can’t decide if you are just venting, asking for civil ways to counter this question when it is put to you, or something else.

Robert Butler replied to the topic 2^2 Factorial Design with Center Points – Curvature Detected in the forum Methodology 2 weeks ago

Well, there’s more to it than that. It is correct that you cannot use the generic curvilinear expression for purposes of prediction because there isn’t any way to assign that response to either of the two variables you have. This means, for purposes of prediction, the best you can do is an equation with mains and interaction. However, you do…[Read more]

Robert Butler replied to the topic 2^2 Factorial Design with Ctr Points – Curvature Detected in the forum Methodology 2 weeks, 3 days ago

There are two schools of thought concerning main effects and interactions – one school says if the interaction is significant you need to keep the main effects and the other one says you don’t.

As for the curvature:

a) I don’t see that term in your model

b) Assuming the equation is a typo – the curvature is generic which means all you know is…[Read more]

Robert Butler replied to the topic Minimum Number of Data Points on a Control Chart? in the forum Tools & Templates 1 month ago

No, I’m afraid this discussion is not an example of a complete misunderstanding of a control chart – Wheeler and Chambers know their stuff.

I agree with 5 data points I can’t apply all of the control chart tests but I can do this – I can get an estimate of the ordinary process variance by employing the method of successive differences, I can get…[Read more]

Robert Butler replied to the topic Minimum Number of Data Points on a Control Chart? in the forum Tools & Templates 1 month ago

As others have noted – more data points are better when it comes to assessing out of control and for all of the reasons already mentioned. However, waiting until you have more (we will arbitrarily define “more” as at least 20 data points) presumes the time/money/effort needed to get more data is forthcoming. I’ve worked on any number of p…[Read more]

Robert Butler replied to the topic Why Shouldn’t We Include Spec Limits in Control Charts? in the forum Tools & Templates 1 month, 1 week ago

Well @Straydog and @Mike-Carnell that guy @chebetz has found us out! I guess it’s time we ask Mike Cyger to tell Katie to change our screen names again. I think I’ll go with Dr. Theodore Sabbatini this time around. :-)

I can’t answer for Straydog or Mike but given our interactions over the years I’m pretty sure their answer will be the same a…[Read more]

Robert Butler replied to the topic Why Shouldn’t We Include Spec Limits in Control Charts? in the forum Tools & Templates 1 month, 1 week ago

I don’t see any reason why you can’t if you want to. In most instances though the question will be: which customer spec limits are you going to include on your chart? I worked in industry for many years before shifting over to medicine and I can’t recall a single product where we were making something for just one customer.

There is also the i…[Read more]

Robert Butler replied to the topic Statistical Power for Two Samples T-Test in the forum Tools & Templates 1 month, 2 weeks 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 1 month, 3 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 1 month, 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

15-year-old 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 2 months, 1 week 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 2 months, 1 week 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 2 months, 1 week 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 2 months, 1 week ago

Robert Butler replied to the topic Need Help with Factorial Design LSSBB Practice Question in the forum Tools & Templates 2 months, 1 week 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 2 months, 1 week 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 2 months, 1 week ago

Robert Butler replied to the topic Probability of an Average for a Group Based on Individual Value Distribution in the forum Tools & Templates 2 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 General 2 months, 2 weeks 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]

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