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    Lengths of slow worms (mm) Frequency
    125-139 / 4
    140-154 / 4
    155-169 / 2
    170-184 / 7
    185-199 / 20
    200-214 / 24
    215-229 / 10
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    are they asking for the mean or S.D maybe ?
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    (Original post by the bear)
    are they asking for the mean or S.D maybe ?
    Find the interquartile range.
    sorry for not including that
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    maybe draw a cumulative frequency curve and get it from there ?
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    (Original post by Elehin)
    Find the interquartile range.
    sorry for not including that
    You need to find the difference between the 25th percentile and the 75th percentile.
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    (Original post by the bear)
    maybe draw a cumulative frequency curve and get it from there ?
    It's something to do with Interpolation.
    You first calculate the lower frequency and finding the Value of Q1, then the same for Q3.
    I'm not sure where i went wrong as the answer i got is too big.
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    (Original post by Elehin)
    Lengths of slow worms (mm) Frequency
    125-139 / 4
    140-154 / 4
    155-169 / 2
    170-184 / 7
    185-199 / 20
    200-214 / 24
    215-229 / 10
    Find the value for n/4, 3n/4, use interpolation for both and substract the answers for the upperquartile (3n/4) by the lower quartile (n/4)
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    (Original post by Elehin)
    It's something to do with Interpolation.
    You first calculate the lower frequency and finding the Value of Q1, then the same for Q3.
    I'm not sure where i went wrong as the answer i got is too big.
    Post your working and we can check it.
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    (Original post by kkboyk)
    Find the value for n/4, 3n/4, use interpolation for both and substract the answers for the upperquartile (3n/4) by the lower quartile (n/4)
    I did exactly those steps but got the wrong answer.
    Here's my steps

    LQ is 71/4 = 17.75 ,round this to 18
    Find where 18 lies on the table.

    M - 184.5 / 199.5-184.5 = 18 - 7/ 20 - 7

    This gives 446.5

    UQ IS 71*3/4 = 53.25

    m - 199.5 / 214.5 -199.5 = 53.25 - 20 / 24 - 20
    This gives 124.6

    UQ - LQ gives a negative number ?
    where did i go wrong ?
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    (Original post by Elehin)
    I did exactly those steps but got the wrong answer.
    Here's my steps

    LQ is 71/4 = 17.75 ,round this to 18
    Find where 18 lies on the table.

    M - 184.5 / 199.5-184.5 = 18 - 7/ 20 - 7

    This gives 446.5

    UQ IS 71*3/4 = 53.25

    m - 199.5 / 214.5 -199.5 = 53.25 - 20 / 24 - 20
    This gives 124.6

    UQ - LQ gives a negative number ?
    where did i go wrong ?
    Can you upload a picture of your working since I can't understand much here, sorry

    The problem is in your linear interpolation:

    I'd use Lower boundary x class width x (how far into the group the mean lies)/frequency
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    (Original post by kkboyk)
    Can you upload a picture of your working since I can't understand much here, sorry

    The problem is in your linear interpolation:

    I'd use Lower boundary x class width x (how far into the group the mean lies)/frequency
    Won't be able to provide a picture at this moment.
    The method which i have used is correct from looking at examples from the Edexcel book , however i don't seem to know where i went wrong.

    Can you just do the question for me? I already know what the answer is but i don't seem to know the process of getting it.
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    (Original post by Elehin)
    Won't be able to provide a picture at this moment.
    The method which i have used is correct from looking at examples from the Edexcel book , however i don't seem to know where i went wrong.

    Can you just do the question for me? I already know what the answer is but i don't seem to know the process of getting it.
    Just found this.

    It's against the forum rule to post full solutions as people will take advantage of this, and would not develop themselves in Mathematics.
 
 
 
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