• So, Voice of the Customer (VoC) is often gathered (one would hope) in the Define phase of a DMAIC process. Before you go out and do that, however, you need to define what process you are working on — for that, a basic SIPOC diagram is good. Once you’ve defined the process and the associated customers, then (and it sound like this) if your…[Read more]

  • Your definitions are correct for a 1-sample t test. However, is that the test you want to run? Don’t you want to run a test comparing your baseline data and variation with your pilot data and variation to see if you’ve made a significant impact? That is, is the 30-day time point the most important part of the study (you have to hit 30 days as…[Read more]

  • Can you really use the mean as a measure of central tendency with discrete data? A mean is used for continuous data. 10 years, 3 months ago

  • 1. Sounds like Minitab added some improvements since 13 – in 15 you can select your distribution. Can you upgrade? I hear 16 is almost out – you might call Mini and ask for timing.

    2. I also hate the “long term” vs “short term” designations – it tends to throw students off. I try to blow past that as quickly as possible and focus on the…[Read more]

  • So, let’s put on our critical thinking caps here. Is there any reason to back up the above statement besides it being cooly dramatic? What quantitative data is the author(s) providing? 10 years, 3 months ago

  • Does that include the 1.5 sigma shift or no? 10 years, 3 months ago

  • I don’t know about 7200, but at N> 7680 you don’t have to correct for small populations. 10 years, 3 months ago

  • That was a greatly useful comment — thanks for your enlightenment and supporting data! 10 years, 3 months ago

  • And the reason we don’t get Cpk in non-normal process capabilities is that the magic d2 constant was based on a normal distribution. No worries, just go with Ppk and potentially explain in terms of ppm or percentage out of spec limits if Ppk is confusing to your audience. 10 years, 3 months ago

  • I would recommend reducing the variation first; then you will have a good idea on how inaccurate you are. Moving a tightly controlled process to correct for bias should be easier than trying to correct an imprecise process for bias, the reducing variation. 10 years, 3 months ago

  • Actually, your data does not need to match a normal distribution for process capability. You’ll see in minitab an option for process capability – non-normal. If you know your distribution, you can select it in the non-normal option in a drop-down menu.

    If your data is not in control, understand and eliminate any special causes before you do…[Read more]

  • For main effects only (and making the dangerous assumption that you don’t have any two-way interactions), go for a resolution III DOE, which is your 8-run solution. Why do a replicate for a screening design? Spend your money later on. The PB may get you a little more data, but I’m not totally sure it’s worth the extra four runs. 10 years, 4 months ago

  • Cathy wrote:

    Darth, what do you think of the avatar? I thought it best to keep with the popular theme “science fiction characters whose names begin with D.”

    Hah — Excellent that I am “In the club!” :P 10 years, 4 months ago

  • Oh dear, my infinite respect for Darth has dropped down a hair — can’t even recognize a Star Trek uniform….I’m not sure if the 3 minute delay is acceptable or not… Don’t you ever get out of your universe? Heavens, what if someone used a Battlestar Galactica avatar? 10 years, 4 months ago

  • The amount of time the website takes to load with all the helpful graphics appears to be significantly longer (although I can’t run a hypothesis test without time travel capabilities), so it is somewhat tedious to flip through multiple conversations; also a bummer. 10 years, 4 months ago

  • Just for the heck of it, why don’t you try an I-MR chart? Your counts are so high, and your percentage is so high, that you may be able to treat the data as continuous. Try plotting each week’s percentage in an I-mR chart and see what happens. 10 years, 4 months ago

  • Can you tell us if the data is for defectives (good parts vs bad parts) or defectives (number of errors in a lot)? Also, could you make up a number that shows the general idea of % (i.e., typically in a week you see 5 out of 1,000 defects, or is is 200 / 1,000 defects)? All these things have an effect. 10 years, 4 months ago

  • Well, if it is population data, then you have a hard number of increase or decrease — you don’t need statistics to infer to the population. The “alarming or not alarming” then becomes a business decision.

    With only two data points, I don’t think you can make a call. You need a greater period of time to see if the increase (or decrease)…[Read more]

  • Don’t forget “evil Anakin” – cute as a kid, really annoying as a teenager, highly dangerous as an adult. Seems appropriate to me…. 10 years, 4 months ago

  • The sad thing is that I have seen software (not Ms Mini, of course) that allows you to put spec limits on control charts. They’re trying to be helpful, like Microsoft…. 10 years, 4 months ago

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