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Practical Quality Engineering Resources Pk Ppk Short and Long Term Capability 2016-02-22

Definitions of long and short term capablity

  1. Bev D

    Bev D Moderator Staff Member

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  2. Miner

    Miner Moderator Staff Member

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  3. ncwalker

    ncwalker Well-Known Member

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    In Wherler's article, both Ppk and Cpk have 6s in the denominator. Shouldn't that be 3s?
     
  4. Miner

    Miner Moderator Staff Member

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    Notice that he added a 2 in the numerator.
     
  5. ncwalker

    ncwalker Well-Known Member

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    I did. And now that you say it, it makes sense. But when I originally looked at it I took his meaning of "2 DNS" to be check BOTH "Distance to Nearest Specification". Not 2 times the Distance to Nearest Specification (DNS). Which would be redundant because "Distance to Nearest Specification" implies you would be checking both sides.

    So yes. Math works out in my head now. But it could have been more clear. Like maybe a multiplication symbol ....
     
  6. Miner

    Miner Moderator Staff Member

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    It depends. Which is clearer?
    a) Y = 2 + 3X - 5X^2
    b) Y = 2 + 3*X - 5*X^2

    Sometimes the multiplication symbol clarifies, sometimes it muddies the waters.
     
  7. ncwalker

    ncwalker Well-Known Member

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    Well, if you want to argue, ;-)

    YOU'RE example is clear. Because it is "3X" and "5X". What Wheeler had would have been "3 X" and "5 X". Which looks like something is missing OR it is enumeration. :)
     
  8. ncwalker

    ncwalker Well-Known Member

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    And I would also posit, it never muddies the waters. It may visually appear messier, but that's not the same as clarity of an equation. It always makes it more clear when you don't take the accepted shortcuts in math.
     
  9. ncwalker

    ncwalker Well-Known Member

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  10. Candi1024

    Candi1024 Well-Known Member

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    Wow, I love that video! You know I never remember learning PEMDAS. If I did it certainly wasn't repeated over and over. But I was taught 3+(-2) = 1 very early on. Now I get it, my teachers knew what they were doing! Thank god for great teachers. If only they were still allowed to actually teach.

    I do remember being taught to do (parenthesis) then (multiplication and division) then (add and subtract) - but nothing about adding before subtracting. I was taught to go from left to right outside of those rules.
     

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