iSixSigma

Robert Butler

Activity

  • To do things like this you really need to spend the money, purchase some good books on experimental design, and read them and keep them close by as a reference.

    The two I would recommend are:

    1. Understanding Industrial Designed Experiments by Schmidt and Launsby

    2. The Design and Analysis of Industrial Experiments by Davies

    To your point -…[Read more]

  • If your question is how do you get the percentages at the bottom of the page the answer is you need information that is not present on the spreadsheet you provided. In order to get the percentages at the bottom you need to know how the efforts are apportioned to each of the consultants. The best you can do with what you have is compute total…[Read more]

  • @cseider – well, welcome back…question – your elapsed time for your most recent group of responses is 62 minutes, 57 minutes, 14 minutes, 8 minutes, and 7 minutes….what happened between 57 and 14?  Lunch break?  :-)

    Take Care

    P.S. where I work the IT department is really on the ball as far as fighting Covid is concerned.  This morning I lo…[Read more]

  • I’m not sure I understand what you mean by “statistical tools to create a baseline.”  Baseline data is just that – data gathered from a process before you attempt to make changes.  As for the data gathering itself – that is an entirely different matter.

    1. How often – I’ll take everything I can get with as much detail as I can get. This means i…[Read more]

  • In summary:

    1.    [The defects are] not deep enough emboss thickness, not enough stretching, or telescoping or collapsing rolls (and what is telescoping and collapsing – are these other ways of expressing not enough stretching or are they something else?

    2.    We know that a majority of these defects are caused by incorrect tension during…[Read more]

  • It looks like your plotting routine for the histogram is running some kind of default binning which is giving you a false impression of your data.  If you look at the linear plot of the data the histogram should have vertical bars at the same places -15, -10, -5, 0 , 5, 10, 15 but it doesn’t. Rather the histogram looks like the bars are at…[Read more]

  • @Straydog is correct – no subgrouping here just the individual data points.  Once you have a histogram built as he recommended (I’d also recommend plotting the data on a normal probability plot) post the graphs here and perhaps I or @Straydog or someone else may be able to offer additional thoughts. 4 months, 1 week ago

  • The central limit theorem applies to distributions of means so, the fact that the distribution of your means passes the Anderson-Darling test isn’t too surprising.

    I’m not trying to be nasty or mean spirited here but the bigger issue is a basic mistake you have made – your post suggests you didn’t take the time to really examine your data. As…[Read more]

  • I think you are still misunderstanding the issue of sample size. Your statement “…covers 80% of the population with 95% confidence…” has no meaning.

    Let’s pretend you have done all of the usual things you need to do with respect to visually inspecting the distribution of those 100 samples (histogram, data on a normal probability plot, time…[Read more]

  • As written, the answer to your question is to sample 80% of the data – there’s no estimation involved.

    Sample size questions focus on moments of a distribution (things like means, standard deviations, etc.)of a sample and are phrased in the following manner: How many samples do I need to take in order to be certain that the mean/standard…[Read more]

  • @KatieBarry Ah Ha! So it IS resurrect old threads month!!!  :-)

    I’m sorry to have to admit this but I don’t think I’ve ever checked the newsletter. Thanks for the heads up. 5 months ago

  • @KatieBarry – is this resurrect old threads month?  This isn’t a complaint – just wondering. 5 months ago

  • Minitab is great so I’m sure they appreciate the 2020 tip of the hat in their direction but this thread has been dormant since 2013 so the original poster might be a bit slow in responding.  :-) 5 months, 1 week ago

  • There isn’t a simple guideline. Which one of  the design methods you use will depend on what it is that you want to do and the kinds of variables you have.

    For example:

    1. Are the variables of interest continuous (or can they be treated as continuous), are they nominal, or are they a mixture of the two?

    2. Are you trying to assess…[Read more]

  • If you have multiple responses then presumably you have a predictive equation for each of those responses.  If that is the case then you should have a minimum and a maximum level of desirability for each response.  If this is true then take your equations – put them in a program, assemble the matrix of X’s and run the equations against the m…[Read more]

  • So if I’m understanding correctly the question you are asking is how to generate a fit to the data in your plot that will be in the form of a predictive equation.

    If that’s the case then, based on just looking at the plots, my first try would be a simple linear regression using the terms pipe motion, the square of pipe motion, stiffness and the…[Read more]

  • I’m missing something.

    The idea of an experimental design is that you have little or no idea of the functional relationship (if any) between variables you believe will have an effect on the output and the level(s) of the output itself.  You put together a design which consists of a series of experimental combinations of the independent variables…[Read more]

  • Maybe we are just talking past one another but I’m not sure what you mean by “the numerical output from the process creates the shape of the model.”

    A random variable is a function that takes a defined value for every point in sample space. – Statistical Theory and Methodology in Science and Engineering – Brownlee – pp. 21.  Given this I would…[Read more]

  • Based on what you have posted the short answer to your question is – no – DOE won’t/can’t work in this situation.

    The factors in an experimental design require either the ability to change the levels of each factor independently of one another or, in the case of mixture designs, to vary ratios of the variables in the mix.  In your situation you…[Read more]

  • I’m not sure what you mean by the regular rules.  If you mean the issue of control limits based on standard deviations about the means then you can still use them.  The issue is one of expressing the data in a form that will allow you to do this.  When you have an absolute lower bound which is 0 the usual practice is to add a tiny increment to th…[Read more]

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