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    • #5825
      Lori Snetsinger
      Participant

      Basic Black Belt Study Guide (Free)

      Hello there,

      I am currently studying for my CSSBB exam, and I am having some trouble with the Primer practice questions in section 7, primarily #s 7 and 33. Question 7 reads: The report Cpk for a process with an average of 28, a spread of 10 units, and USL and LSL of 35 and 15, respectively would be:

      a. 1.6
      b. 1.4
      c. 1.8
      d. .714

      I have no idea how to estimate the standard deviation given this information, as “spread” isn’t covered anywhere in the Primer section. Please help!

    • #5848
      waardg
      Participant

      Basic Green Belt Study Guide (Free)

      Cpk = MIN [(USL – mu) / 3 sigma)] ; [(mu – LSL)/3 sigma)]
      sigma = Rbar / d2
      Rbar = 10, d2 comes from a table. (R= Range = Spread)

    • #5849
      Lori Snetsinger
      Participant

      Basic Black Belt Study Guide (Free)

      The problem is that I don’t have the value for n to be able to look up the d2 value.

    • #5924
      Ted Hessing
      Keymaster

      Six Sigma Study Guide Support
    • #5935
      joey1202
      Participant

      Six Sigma Study Guide Alumni

      Which d2 should be used using this table since n is unknown?

    • #5937
      Lori Snetsinger
      Participant

      Basic Black Belt Study Guide (Free)

      I found an answer to this on the interwebs, here’s an excerpt, as well as the link:
      In the question process spread is given 10 units… And you have taken it as standard deviation directly….
      This process spread of 10 units is assumed to be 6 sigma. Thus sigma is 10/6.

      http://www.cram.com/flashcards/ss-stats-formulas-equations-5453251

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