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Skewness....Help plz

  • 13-01-2009 11:16am
    #1
    postalservice
    Registered Users, Registered Users 2 Posts: 362 ✭✭


    Hi there,
    I have a project due tomorrow and i am stuck on one part.

    We were given data based on test results of a class of 100 students
    I calclulated the skewness value to be 72.4, mean of 38.6, median of 35.4 and mode of 32.5...and they are correct
    The final part of the section however asks......
    "A second class of 100 students took the same exam and a skewness value of minus 10 was calculated from their marks. Can you determine which class did better overall in the exam? Explain."

    Any help would be greatly appreciated. Thanks:o


Comments

  • #2
    gerry87
    Registered Users, Registered Users 2 Posts: 872 ✭✭✭gerry87


    postalservice wrote: »
    Hi there,
    I have a project due tomorrow and i am stuck on one part.

    We were given data based on test results of a class of 100 students
    I calclulated the skewness value to be 72.4, mean of 38.6, median of 35.4 and mode of 32.5...and they are correct
    The final part of the section however asks......
    "A second class of 100 students took the same exam and a skewness value of minus 10 was calculated from their marks. Can you determine which class did better overall in the exam? Explain."

    Any help would be greatly appreciated. Thanks:o

    Well the second class has fatter negative tails, so more students scoring extremely below average. You can't really tell which class did better overall unless you have the average. The first class could be really positively skewed with an average of 20% while the second class could be negatively skewed with an average of 80%.

    Even then you would have to determine whats meant by "better", higher average? More students passing? More students scoring really high?


  • #3
    postalservice
    Registered Users, Registered Users 2 Posts: 362 ✭✭postalservice


    That's exactly what i thought. But our lecturer said one was better and i was like:confused:.

    Just e-mailed her there anyway.
    thanks


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