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Math Help - Homework help!

  1. #1
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    Apr 2012
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    Ireland
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    Homework help!

    Three variables (X1, X2 and X3) were recorded for a sample of 20 people taken from
    attendees of a course. X1 is nationality (1=Irish, 2=English, 3=Welsh, 4=Scottish), X2
    is a score on an entrance exam (out of 8) and X3 is time (seconds) spent doing a task.


    X1 X2 X3
    2 5.2 15.4
    4 5.7 16.1
    1 5.4 12.4
    3 6.2 13.4
    1 5.8 15.6
    2 4.3 16.8
    2 5.2 16.8
    1 5.7 14.9
    2 6.5 16.7
    4 5.5 16.0
    1 5.4 5.1
    2 5.9 9.1
    1 6.2 14.6
    4 4.3 13.5
    4 4.7 13.8
    4 4.6 18.3
    1 4.9 12.2
    2 5.6 17.4
    3 6.4 17.6
    1 5.4 16.9


    For each of X1, X2 and X3,
    (a) Sketch an appropriate graph to display the distribution of the variable.


    (b) Use an appropriate method to determine if there are any outliers. Show any workings.

    This is my question which i really just cant understand! what graphs should i draw! i drew a bar chart for x1 but i am completely lost for x2? and for question b is the graph an appropriate method?

    Thanks for any help
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  2. #2
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    Joined
    Apr 2012
    From
    Minnesota
    Posts
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    Re: Homework help!

    A bar chart would be appropriate for X1; I would recommend histograms for X2 and X3.

    While you could perhaps guess outliers based on the graph, it would be better to perform some calculations. There is no absolute requirement here; however, a good rule of thumb is to look for outliers >1.5 times the interquartile range from the 25th and 75th percentiles. The IQR is equal to the 75th percentile minus the 25th percentile.

    I will leave the work as an exercise for you...but as a hint, X3=5.1 is the outlier.
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