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Math Help - Mean

  1. #1
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    Mean

    Hey,

    Can you guys explain these questions:

    60% of the mark is term work and 40% is exam

    If yoiu receive a final mark of 76, and receive 70 on the exam, what is your term mark? (All marks are out of 100)

    Can you guys explain how you would get the answer? Does it have something to do with weighted mean?

    ------------------------------------

    The mean of a set of numbers is 26, What would the mean be if one of the numbers was increased by 10?



    Thankyou
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  2. #2
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    Also, what is the difference with a population mean and a sample mean?
    Thanks
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  3. #3
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    Quote Originally Posted by NineZeroFive View Post
    Hey,

    Can you guys explain these questions:

    60% of the mark is term work and 40% is exam

    If yoiu receive a final mark of 76, and receive 70 on the exam, what is your term mark? (All marks are out of 100)

    Can you guys explain how you would get the answer? Does it have something to do with weighted mean?
    final = 0.6*term + 0.4*exam

    so:

    76 = 0.6*term + 0.4*70

    rearranging:

    term = (76 - 0.4*70)/0.6 = 80.


    ------------------------------------

    The mean of a set of numbers is 26, What would the mean be if one of the numbers was increased by 10?



    Thankyou
    Mean = sum/N

    if one of the numbers is increased by 10 the new sum s'=s+10, and the
    new mean:

    mean'=s'/N=(s+10)/N = mean + 10/N

    RonL
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  4. #4
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    Quote Originally Posted by NineZeroFive View Post
    Also, what is the difference with a population mean and a sample mean?
    Thanks
    We have a population which might be the heights of all the inhabitants of
    Springfield, this with luck will have a mean, we call this the population mean.

    We draw a sample of 100 of the inhabitants and calculate their mean height,
    this is the sample mean.

    RonL
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  5. #5
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    Quote Originally Posted by CaptainBlack View Post
    final = 0.6*term + 0.4*exam

    so:

    76 = 0.6*term + 0.4*70

    rearranging:

    term = (76 - 0.4*70)/0.6 = 80.




    Mean = sum/N

    if one of the numbers is increased by 10 the new sum s'=s+10, and the
    new mean:

    mean'=s'/N=(s+10)/N = mean + 10/N

    RonL
    Sorry, I forgot to add that there are 5 numbers in the set.

    Can someone please explain this ?

    Thanks
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  6. #6
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    Quote Originally Posted by NineZeroFive View Post
    Sorry, I forgot to add that there are 5 numbers in the set.

    Can someone please explain this ?

    Thanks
    So N=5, and then:

    mean' = mean+10/5 = mean+2

    RonL
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  7. #7
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    Quote Originally Posted by CaptainBlack View Post
    So N=5, and then:

    mean' = mean+10/5 = mean+2

    RonL
    Sorry, I'm not to good with math..

    How is mean' different from mean?

    Can you please calculate it for me? Thankyou

    Also, regarding my first question, can you please show me how the equation gets rearranged? Thanks.
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  8. #8
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    Quote Originally Posted by NineZeroFive View Post
    Sorry, I'm not to good with math..

    How is mean' different from mean?

    Can you please calculate it for me? Thankyou

    Also, regarding my first question, can you please show me how the equation gets rearranged? Thanks.
    mean is the original mean and mean' is the mean when one value is increased by 10.

    RonL
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  9. #9
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    Quote Originally Posted by CaptainBlack View Post
    mean is the original mean and mean' is the mean when one value is increased by 10.

    RonL
    I get 7.2 :S
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  10. #10
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    Quote Originally Posted by NineZeroFive View Post
    I get 7.2 :S
    mean'=mean+2=26+2=28

    RonL
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  11. #11
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    Quote Originally Posted by CaptainBlack View Post
    mean'=mean+2=26+2=28

    RonL
    Why did you add 2?
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  12. #12
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    Quote Originally Posted by NineZeroFive View Post
    Why did you add 2?

    Because:

    mean'=s'/N=(s+10)/N = mean + 10/N

    and mean=26, and N=5.

    RonL
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