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anonymous

  • one year ago

Suppose the number of students in a class for the Business Statistics program at a University has a mean of 23 with a standard deviation of 4.3. If 15 classes are selected randomly, find the probability that the mean number of students is between 20 and 30. 0.9699 0.9966 0.8412 0.6824

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  1. anonymous
    • one year ago
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    @sweetburger

  2. anonymous
    • one year ago
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    @UsukiDoll

  3. UsukiDoll
    • one year ago
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    I haven't studied statistics. Sorry :/

  4. anonymous
    • one year ago
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    is okay

  5. phi
    • one year ago
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    These are the population statistics: mean of 23 with a standard deviation of 4.3. \[ \mu = 23 ,\ \ \sigma= 4.3\] 15 classes are selected randomly represent a sample of size 15. The mean of this sample is also 23, but with a standard deviation \( \sigma_{sample}= \frac{1}{\sqrt{15}} \sigma\)

  6. phi
    • one year ago
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    the std dev of your sample means will be 4.3/sqrt(15) = 1.11 the limits 20 to 30 represent -3/1.11 to +7/1.11 or -2.7 to +6.3 std dev as the +6.3 above the mean is very far out in the tail, you can just find the area under the curve from -2.7 to infinity (or 1 - area below -2.7)

  7. anonymous
    • one year ago
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    @phi and how would you find the area under the curve ?

  8. phi
    • one year ago
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    people use a z table.

  9. anonymous
    • one year ago
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    so can i find it and tell you my answer to see if i get it right ?

  10. anonymous
    • one year ago
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    so i got C but i dont think that is correct

  11. phi
    • one year ago
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    you are looking for the area |dw:1437654513070:dw|

  12. phi
    • one year ago
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    can you post a copy of the table you are using ?

  13. anonymous
    • one year ago
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    i dont have one i just looked one up in google

  14. anonymous
    • one year ago
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    i honestly just dont get this and i already went back to the lesson like 3 times to see if i could figure it out and i cant.

  15. phi
    • one year ago
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    what is the link to the table?

  16. anonymous
    • one year ago
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    http://cosstatistics.pbworks.com/f/1281154582/6368.png

  17. anonymous
    • one year ago
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    wait would it be B ?

  18. phi
    • one year ago
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    the area you want for your problem starts at -2.7 and goes to the right your table shows the area starting on the left and going up to some std dev. this is opposite of your problem. BUT, because the curve is symmetric, you can use this table. find the value for z= 2.7

  19. anonymous
    • one year ago
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    so where it say 2.7 i got there ?

  20. phi
    • one year ago
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    yes

  21. anonymous
    • one year ago
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    i got 0.9966

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