Amit Kumar Ojha


  • Congratulations ce_seek. You’re welcome. I’m glad I was able to be of some assistance. 2 weeks, 2 days ago

  • No, you do not need a minimum of 30 samples – Gossett put that bit of nonsense to rest back around 1908 or so. Other than the fact that the basic Cpk calculations require data normality there is no connection between 30 samples and normality. Take what you have and press on with the calculation. If you are really concerned about the structure of…[Read more]

  • You can do a capability analysis on attribute data. Check Chapter 9 – Measuring Capability with Attribute Data in the book Measuring Process Capability by Bothe – you can probably get the book through inter-library loan. 2 months, 3 weeks ago

  • I’m not trying to be rude or offensive but the short answer to your question is – start over.

    1. You will need to provide more information concerning the QA score – what is it and how is it quantified?
    a. Is this some kind of personal assessment by yourself – i.e. a 1-10 Likert score based on perception or is it something that is…[Read more]

  • Something else to consider – are you sure the issue is one of just confirming a known error rate of 8% and not one of knowing, with a high degree of certainty, if the error rate has changed from say 8% to 9%? If it is the latter then you would need about 30000 samples to confirm this kind of shift with 80% power and an alpha of .05. 6 months, 3 weeks ago

  • If the defects are actually random and are randomly distributed throughout the year then, from time to time, you could take a random sample of 50 invoices and check to see if you have approximately 4 errors. In order to determine how often you should take a random sample you should take the data from the last year (we are assuming it is in time…[Read more]

  • I have no idea what a .mpj file is but it won’t open in anything I have – try saving it as an Excel file and maybe I or someone else might be able to offer some advice. 7 months, 1 week ago

  • You will need to provide more detail with respect to dies and rotary indexing stations before anyone can offer much in the way of advice. Is this a situation where there are X number of dies with 4 cavities each in Y number rotary indexing stations or are dies and rotary indexing stations two completely different and separate things that can be…[Read more]

  • The short answer to your question is there aren’t any tests like that. In order to make a meaningful comparison of any kind you need context. Comparing one single number with another single number is a comparison devoid of context. The only thing you can say about any observed difference between two single numbers is a difference exists.

    The…[Read more]

  • Is there any way of getting this done? – Yes, start over because, based on your description of what you are doing, you are a very long way from being able to make any kind of decisions concerning employee performance.

    Let’s do a recap of your initial post.

    1. You said,”We convert the survey responses into continuous data (ex.: Liker scale 1 to…[Read more]

  • My guess would be your friend did something wrong in Minitab. If you don’t have subgroups then there is no within to use for calculations. Is there any chance the standard deviation it did compute was either just the sample standard deviation of all 60 points or the standard deviation of the mean of the 60 data points? 11 months, 1 week ago

  • A Google search will provide you with what you need.

    Here’s one I found for Cpk 11 months, 1 week ago

  • When you say you “have a lot of Attribute data for my analysis (Pass/Fail)” there isn’t much anyone can offer because that statement doesn’t tell anyone what you mean by “a lot.”

    However, if we make the following assumptions:
    1. You take grab samples of a given size from your production process and you inspect each item in the sample…[Read more]

  • Addendum – I played around with the data you posted and I must admit I don’t see how Minitab generated those estimates. The average of the non-missing data is -14.1 and the standard deviation of the non-missing data is 90.9 which means your 2 sigma limits would be (upper) = -14.1 +2*90.9 = 167.7 and the lower would be -195.9.

    If I substitute…[Read more]

  • A missing value is a missing value – what you have done is construct an entirely different set of data with a lot of average values in place of the original missing values. Under these circumstances you should expect to get something different because the two data sets are not equivalent.

    I don’t have Minitab but my guess is that Minitab is…[Read more]

  • As written, your post doesn’t provide enough information concerning your objective. My guess is that you are looking for tester agreement when running tests on split samples but maybe not. If you are looking for agreement then that is not the same thing as correlation and you will need more than a simple check of correlation to determine…[Read more]

  • It looks like excel is just computing the standard deviation of the sample and then giving you the plus/minus 2 standard deviations of the sample whereas Minitab looks like it is computing USL and LSL spec limits 1 year ago

  • @Darth – things are going well here – how about you and yours? 1 year ago

  • Given what you have posted, I think you are faced with one of two scenarios.

    (In order to provide some clarity with respect to what follows let’s pretend the treatment has as part of its application changes in temperature and pressure. Given this then there are at least two different versions of “no treatment”.)

    1. The situation for “no…[Read more]

  • Darth is correct. Here’s the relevant quote from a standard statistics text.

    Applied Regression Analysis 2nd Edition – Draper and Smith pages 22 and 23

    “[with regard to regression] Up to this point we have made no assumptions at all that involve probability distributions. A number of specified algebraic calculations have been made and tha…[Read more]

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