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Math Help - Normal Distribution question

  1. #1
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    Normal Distribution question

    A consumer agency suspects that a cereal company is under¯lling packages for one of its brands. The package label states `750 grams net weight'. Experience has shown that the package weights are normally distributed with a standard deviation of 5.2 g. A random
    sample of 15 packages yields a mean weight of 747 g.
    (a)
    Is there suffcient evidence to indicate that the true mean weight is lower than advertised? Support your answer with an appropriate hypothesis test and state yourconclusions clearly.

    i know that the answers is that the true mean weight is less than advertised, but no-one has explain it to me properly can some one help???

    (b)
    Sketch the distributions of weights and average weights (based on 15 packages) on the same graph. Shade or indicate the area represented by the p-value.

    How can i do this without actual sample weights???

    Sorry if these question seem really simple, but i feel like i am getting the asnwers thrown at me with out a simple explanantion.

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  2. #2
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    Quote Originally Posted by ashvuck View Post
    A consumer agency suspects that a cereal company is under¯lling packages for one of its brands. The package label states `750 grams net weight'. Experience has shown that the package weights are normally distributed with a standard deviation of 5.2 g. A random

    sample of 15 packages yields a mean weight of 747 g.


    (a)
    Is there suffcient evidence to indicate that the true mean weight is lower than advertised? Support your answer with an appropriate hypothesis test and state yourconclusions clearly.

    i know that the answers is that the true mean weight is less than advertised, but no-one has explain it to me properly can some one help???

    (b)


    Sketch the distributions of weights and average weights (based on 15 packages) on the same graph. Shade or indicate the area represented by the p-value.

    How can i do this without actual sample weights???

    Sorry if these question seem really simple, but i feel like i am getting the asnwers thrown at me with out a simple explanantion.


    Start by getting the distribution for the sample mean. It will be in your textbook, class notes and can be found using Google eg. Sampling Distribution of the Mean

    Then do the appropriate calculation with it and form a conclusion. If you need more help, please say what you've done and say where you get stuck.

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  3. #3
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    Hi mr fantasic

    I was told from my class mate to do a hypothesis test is this the same thing? Sorry its still not clicking. I know the sample mean is 1.34
    but am not sure what to do with it ?
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  4. #4
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    Can i use a z-test i found it on the net?
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  5. #5
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    Quote Originally Posted by ashvuck View Post
    Can i use a z-test i found it on the net?
    Yes.
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