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Math Help - statistics - median

  1. #1
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    statistics - median

    How do I work out how to find the new sample mean when you have a sample size of 20, the mean is 12, the data is bimodal with modes of 10 and 17 and the median is 14. After this has all been calculated a new item of data has been found, being of value 17, which needs to be added to the sample. So now the sample size is 21 and I was able to work out the new mean is 12.24 by using the equation - but I can't work out what the new median would be.
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  2. #2
    Member Glaysher's Avatar
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    How many forums have you posted this in?

    Sample size of 21 would make the median the 11th observation

    Did you get the raw data to start with?

    If so, put it into order and stick the new 17 in the appropriate place
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  3. #3
    Grand Panjandrum
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    Quote Originally Posted by bennyya
    How do I work out how to find the new sample mean when you have a sample size of 20, the mean is 12, the data is bimodal with modes of 10 and 17 and the median is 14. After this has all been calculated a new item of data has been found, being of value 17, which needs to be added to the sample. So now the sample size is 21 and I was able to work out the new mean is 12.24 by using the equation - but I can't work out what the new median would be.
    Half the observations should be above and half below the median.

    Without knowing some values about the old median you can't work out
    the new median.

    Here the old median is between the 10th and 11th largest sample values,
    but that 11th largest sample could be as small as 14, and presumably as
    large as 17. Also there could be a number of sample values between 14
    and 17.

    RonL
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    Without the raw data it is not possible to find the median?
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  5. #5
    Grand Panjandrum
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    Quote Originally Posted by bennyya
    Without the raw data it is not possible to find the median?
    Without sufficient information to allow you to deduce what are the central-ish
    data values; yes you can't find the new median.

    RonL
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    Thanks heaps for your help!
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