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Homework Help: Statistics - Binomial Probability question

  1. Feb 14, 2009 #1
    Hi. i keep finding a different answer than what textbook offers. is my answer correct?

    question: the quality control department of a company making computer chips knows that 2% of the chips arw defective. use the nurmal approximation to the binomial probability distribution, with a continuity correction, to find the probability that, in a batch containing 1000 chips, between 20 and 30 chips (inclusive) are defective.

    my answer: probability=0.02
    using TI 84+
    binomcdf(1000,0.02,30)-binomcdf(1000,0.02,19)=0.5179 (its my answer)
    but the textbook says the answer is: 0.5349

    is there anything wrong with my solution? what do you think is the real answer?

    thank you
  2. jcsd
  3. Feb 14, 2009 #2


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    Homework Helper

    You aren't using the continuity correction - you aren't even using the normal approximation.
  4. Feb 14, 2009 #3
    oh. i will work on that.

    turns out my teacher has not said a single word on continuity correction and normal approximation. so i just assumed i could solve it using commulative thing.
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