Intermediate 2 Mathematics - Statistics Question: Help?

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  1. nerd434's Avatar
    1 17-05-2012  21:36
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    • Location: Edinburgh
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    Intermediate 2 Mathematics - Statistics Question: Help?
    I was wondering whether someone on here could walk me through this question? It's the last question in the 2004 calculator paper. It's worth 5 marks so I'm not really sure where to start..

    I can't upload photos to my threads for some reason, the question is here: http://tinypic.com/view.php?pic=315xr9u&s=6
    Last edited by nerd434; 17-05-2012 at 21:48.
  2. tomctutor's Avatar
    2 28-12-2012  20:18
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    • Location: West Lothian
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    Re: Intermediate 2 Mathematics - Statistics Question: Help?
    Been some time - but for sake of consistancy and to help future students i'll try to explain:
    This is what statisticians call Discreet grouped data - it is fair to assume that the mean on each interval is representative of the actual grouped data:
    Rewrite table to work out means..
    \begin{array}{c|r|r|r|} No.of.days (d) & class.mean (\bar{d})& Freq. f & f\bar{d} \\ \hline 0..4& 2 & 14 & 28 \\ 5..9& 7 & 17 & 119 \\ 10..14& 12 & 8 & 96 \\ 15..19& 17 & 4 & 68 \\ 20..24& 22 & 2 & 44 \\ \hline \sum & & 45 & 355 \end{array}

    mean number of days absence = \sum f\bar{d}/\sum f = 355/45 = 7.9 days

    Although the days were quoted as whole days absence it is permissable to quote fractional means!
    Last edited by tomctutor; 28-12-2012 at 20:33.
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