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    For the previous question I got the mean of the weight of 150 babies to be 3.46kg.
    During the same period of time, 18 babies were born in the special care baby unit of the hospital. The mean weight of all 168 babies was found to be 3.35 kg.
    iv) Calculate an estimate weight of the 18 babies in the special care unit
    v) What effect will the addition of the 18 extra data items have on the median and the interquartile range. Explain your answer

    Not sure how to do part v for 3 marks
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    (Original post by imaan567)
    For the previous question I got the mean of the weight of 150 babies to be 3.46kg.
    During the same period of time, 18 babies were born in the special care baby unit of the hospital. The mean weight of all 168 babies was found to be 3.35 kg.
    iv) Calculate an estimate weight of the 18 babies in the special care unit
    v) What effect will the addition of the 18 extra data items have on the median and the interquartile range. Explain your answer

    Not sure how to do part v for 3 marks
    Are the weights normally distributed?
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    if all the original 150 babies weighed 3.46 kg each then putting 18 other babies into the set would not affect the median or IQR at all.
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    (Original post by SeanFM)
    Are the weights normally distributed?
    Erm, the mean weight of the 150 babies is 3.46 kg and the mean weight of the 18 babies is 2.44 kg. The mean weight of all the 168 babies is 3.35 kg. I don't think they are normally distributed
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    (Original post by imaan567)
    Erm, the mean weight of the 150 babies is 3.46 kg and the mean weight of the 18 babies is 2.44 kg. The mean weight of all the 168 babies is 3.35 kg. I don't think they are normally distributed
    Are you sure?

    Did it mention in the previous question that the weight of one baby is normally distributed?

    If so then the mean is also normally distributed

    This is important because you can then say that the median = the mean (a property of the normal distribution). And this is useful, not because you're actually supposed to calculate the new median but because you just need to know which direction the new data takes it in.


    But anyway, think about your current median and what happens when you add a data set with a lower median - will the old median go up or down? Why?

    In maths it is very helpful to use simple examples.

    So if you had the numbers from 2 to 10, the median is 6. Now if you combine that with the numbers 1 2 3, where the median is 2, what is the median of the sets combined? This will help you picture what you need to do.
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    (Original post by SeanFM)
    Are you sure?

    Did it mention in the previous question that the weight of one baby is normally distributed?

    If so then the mean is also normally distributed

    This is important because you can then say that the median = the mean (a property of the normal distribution). And this is useful, not because you're actually supposed to calculate the new median but because you just need to know which direction the new data takes it in.


    But anyway, think about your current median and what happens when you add a data set with a lower median - will the old median go up or down? Why?

    In maths it is very helpful to use simple examples.

    So if you had the numbers from 2 to 10, the median is 6. Now if you combine that with the numbers 1 2 3, where the median is 2, what is the median of the sets combined? This will help you picture what you need to do.
    Ah Ok thankyou so much, I understand now!
 
 
 
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