## Activity

Robert Butler replied to the topic Standard Deviation and Variance in the forum General 1 week ago

I guess I don’t understand why you are bothering with Z scores. To rephrase your question – I have an estimated average travel time of 39 minutes to get to work with a sample standard deviation of 7 minutes.

The question that is being asked is: what kind of reduction in variation of individual travel time must an employee make in order to…[Read more]

Robert Butler replied to the topic Standard Deviation and Variance in the forum General 1 week ago

That has to be one of the worst homework problem statements I think I’ve ever seen. As written there are all kinds of answers and solutions to the problem.

1. If the reported standard deviation is the standard deviation of the mean and not just the sample standard deviation then there isn’t much of anything you can do with the statement…[Read more]

Robert Butler replied to the topic I-MR or X Bar and R Control Chart? in the forum Tools & Templates 1 week, 2 days ago

If by a batch you mean a single run such as contents of one reactor vessel then the answer is neither because those samples are repeated measures – not independent measures. If you try to build any control chart with that kind of data the control limits will be too narrow because the sample-to-sample variability within a single batch is going to…[Read more]

Robert Butler replied to the topic DOE – How to Design Experiment with Multiple Levels in the forum Implementation 1 week, 3 days ago

Which one is better depends on many things. If it is preliminary and you have no prior information concerning a possible curvilinear response over the range of variables you are examining then it comes down to a matter of time/money/effort. If we are discussing the example of your other post – 2 variables, then you would be running 6 vs 10…[Read more]

Robert Butler replied to the topic 2-Factor 4-Level Full Factorial Design Help in the forum Methodology 1 week, 4 days ago

Addendum: With respect to the residual plot. I left out a piece – You want to look at the overall pattern of the residuals – not just where the center points fall. If the model is adequate you should see a random distribution of data points above and below the 0 residual line. As part of that assessment you will want to see how the center points behave.

Robert Butler replied to the topic 2-Factor 4-Level Full Factorial Design Help in the forum Methodology 1 week, 4 days ago

QUESTION 1: is this already okay?

Yes, except as written your point #2 sounds like you are just going to look at a model of X1 and X2 and not bother with including the interaction. The full model would be response = fn(X1, X2, X1*X2). What you want to do is run backward elimination on the full model to see what terms remain in the reduced model…[Read more]

Robert Butler replied to the topic 2-FACTOR 4-LEVEL FULL FACTORIAL DESIGN HELP in the forum Methodology 1 week, 5 days ago

The issue is this – the basic philosophy of experimental design is if you are going to see a difference in response when you change conditions your best chance of seeing that difference is by comparing the results for the extremes of the variables of interest. This is the point of two level factorial designs. Thus, if you take the extremes of…[Read more]

Robert Butler replied to the topic Should I Be Worried Moving from Academia to Industry? in the forum General 2 weeks, 5 days ago

I wouldn’t say “People in charge of hiring rarely understand the steps to getting a PhD and typically lump academics into a group of elitists “sitting in a corner studying to take a test”. Rather, it is a matter of how you present the fact of earning your degree to them.

For example, my first two pieces of paper are in physics. When I went for…[Read more]

Tom Gause and Robert Butler are now friends 2 weeks, 5 days ago

Robert Butler replied to the topic Should I Be Worried Moving from Academia to Industry? in the forum General 2 weeks, 5 days ago

I agree with @mike-carnell as far as the “Wow” factor is concerned – in my experience there isn’t any. I’ve worked in industry and medicine as a physicist, engineering statistician, and biostatistician (oh yes,and as a black belt) for almost 40 years. Except for including the facts and dates of my three degrees on the initial job application form…[Read more]

Robert Butler replied to the topic Binomial process in the forum New to Lean Six Sigma 2 weeks, 5 days ago

As written your question is meaningless. You will need to give some idea of what it is that you are trying to do. For example, if you are running an analysis of some kind and the outcome is productive yes/no where you have an operational definition of “productive” and you are looking for possible relationships between measured inputs and the…[Read more]

Robert Butler replied to the topic Can someone, please, check my math and tell me what I'm doing wrong? in the forum Tools & Templates 3 weeks, 1 day ago

Never mind – it always helps to correctly read your own calculator screen – the sum is .004800 not .004880. When you take the square root of .004800 and divide .04 by that you get .577 which rounds up to .58

Robert Butler replied to the topic Can someone, please, check my math and tell me what I'm doing wrong? in the forum Tools & Templates 3 weeks, 1 day ago

Hmmmmmm…there must be some kind of double precision inside the calculator. If I first sum the two values and take the square root of the sum and do a division of that number into .04 I get the numbers indicated. However, if I just input .00488 and take the square root of that number I get .069857 which when divided into .04 gives .572 which…[Read more]

Robert Butler replied to the topic Can someone, please, check my math and tell me what I'm doing wrong? in the forum Tools & Templates 3 weeks, 1 day ago

.002112 + .002688 = .0048800 and the square root of that is .069282. Divide .04 by that and you get .577350 which when rounded up to the level of precision allowed in your calculation is .58

Robert Butler replied to the topic Can I Create an X-Y Matrix with Some Outputs Dependent from Other Outputs? in the forum General 1 month ago

Just tallying how many times some X variable shows up in a series of regression equations (one for each Y response) isn’t going to address the importance of that X. If we use your example Y1 = X2*X1^2 and Y2 = X2*X1*Y1^2 then, in order for what you are saying to be true, the coefficients for the X’s in both of the models for Y1 and Y2 would have…[Read more]

Robert Butler replied to the topic Average Values in VSM? in the forum Tools & Templates 1 month, 1 week ago

Value Stream Mapping (VSM) is a way to track a process from beginning to end with an eye towards examining the system to look for places for improvement within the process. Your description of what you plan to do isn’t VSM. Indeed, based on your post I’m not sure what it is that you are trying to do.

My understanding of your post is as…[Read more]

Robert Butler replied to the topic Can You Do a Design of Experiments with Different Levels for Different Factors? in the forum Methodology 1 month, 1 week ago

I don’t understand what you mean by “setup in Minitab 18.” The six point design is all there is and it would just be a matter of building the appropriate spreadsheet for the X’s and Y responses. If you go with just the six points you can build a model where Y is a function of A, B, AB, and B*B. If you toss in a single replicate of one of the…[Read more]

Robert Butler replied to the topic Can You Do a Design of Experiments with Different Levels for Different Factors? in the forum Methodology 1 month, 2 weeks ago

Thanks Mike

Robert Butler replied to the topic Can You Do a Design of Experiments with Different Levels for Different Factors? in the forum Methodology 1 month, 2 weeks ago

Thanks Katie(?), for correcting the design display on my first post. You can remove the second one if you wish.

Robert Butler replied to the topic Is a Target Outside Range of Xform Function Bad? in the forum Tools & Templates 1 month, 2 weeks ago

The other option is to not bother with any kind of transformation. Since you know the distribution is non-normal for data when the process is in control just use the usual methods for calculating Cpk for non-normal data. It is my understanding that Minitab has this method as part of the program. The method is described in detail in Chapter 8 of…[Read more]

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