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What about this formulation

  1. Sep 20, 2013 #1
    I'm taking a course in probability and statistics and encountered an exercise with a formulation that doesn't make sense at all to my English-as-second-language ears.

    I will recite the exercise here and maybe you could help my settle wether if the original formulation is bad, or if I've found an opportunity to learn a new way of formulating myself in English.

    The exercise is from "Introduction to Probability and Statistics" by J.Susan Milton and Jesse C. Arnold (McGraw-Hill 2004).

    I'll quote some excerpts that I think will provide enough information.

    Section 3.4, ex. 25:

    The density function is given by

    f(x) = (1-p)x-1*p (geometric)

    where p=.05

    Now (e) doesn't make any sense at all to me. What makes least sense is the use of "that".

    It's solved by

    P(X≥3) = 1-( f(1) + f(2) )

    However, a more appropriate formulation of (e) I then think would be for instance:

    What do you think? Is the original formulation of (e) good, quite inprecise or even incorrect?
  2. jcsd
  3. Sep 20, 2013 #2


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    Homework Helper

    It means, 2 runs produce no unacceptable lots. Therefore you need at least 3 to produce an unacceptable lot. So you want the probability p that the first 2 runs are acceptable.

    It is phrased correctly.
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