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Math Help - standard deviation portions

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    standard deviation portions

    A bakery firm finds that its average weight of the most popular package of cookies is 32.06 ounces with a standard deviation of .1 ounces. what portion of cookie packages will weigh less than 31.9 ounces and more than 32.3 ounces?
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    Quote Originally Posted by jax760 View Post
    A bakery firm finds that its average weight of the most popular package of cookies is 32.06 ounces with a standard deviation of .1 ounces. what portion of cookie packages will weigh less than 31.9 ounces and more than 32.3 ounces?
    First calculate the z-value corresponding to X = 31.9 and X = 32.3. Can you do this?

    Then calculate Pr(Z < z-value for X = 31.9) and Pr(Z > z-value for X = 32.3). Can you do this?

    Add the above two probabilities together and multiply the result by 100 to get the required portion as a percentage.
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    Thats where my problem is, I have about three formulas I can use to calculte the z and I'm not sure which one I should use, is it bermulia i'm not sure i spelled that right.
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    Quote Originally Posted by jax760 View Post
    Thats where my problem is, I have about three formulas I can use to calculte the z and I'm not sure which one I should use, is it bermulia i'm not sure i spelled that right.
    Whatever you're trying to spell is irrelevant to this question. Unless you're trying to spell Z = \frac{X - \mu}{\sigma}.

    Now get the z-values. Then calculate the probabilities. (review the section in your class notes or textbook on calculating probabilities using a standard normal distribution if necessary).
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