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  • Mar 29, 2011, 03:05 AM
    pop000
    Statistics Question
    I found that the:Average,Median,Mode ,and the Variance.
    http://p1cture.me/images/83563902090613820582.jpg
    And now I got new Information that say's that after reviewing exams it was decided to give more 5 point to each student, as long as the test score does not exceed 100.
    How all the indices will changed, there is no need to calculate just respond by understanding .

    So all I know is the Average will get bigger.
    But how can I answer about the other indices?

    Thanks
  • Mar 29, 2011, 06:23 AM
    jcaron2
    As you said, the average will get bigger, but you don't know by exactly how much (because you don't know how many scores were between 96 and 100, and therefore will bump up against the 100 barrier).

    What about the median? If everybody's score goes up by 5 points (except for a few students at the top end of the distribution), what happens to the median?

    As for the mode, what did you get when you calculated it the first time?

    Finally, as for variance, the entire population of students saw their grades increased by 5 points, except for a few students at the top. If not for those few students, the variance wouldn't have changed at all. However, since they ran into the 100 barrier, their grades were effectly pushed slightly lower (closer to the average) compared to the rest of the population. So what does that do to variance?
  • Mar 29, 2011, 12:48 PM
    pop000
    hi thanks you for answering.

    so the median will get bigger .

    about the mode when I calculated it in the first time I got 85 here I think I can't know how it will change yes?

    and the variance will get smaller a little bit.
    do I correct?
    and I can know any of the value of the new indices without calculate?
    thank you again.
  • Mar 29, 2011, 04:35 PM
    jcaron2
    The median will not only get bigger, it will increase by exactly 5 points.

    I'm assuming you posted all the information you were given so I agree with you about the mode; it's not possible to know exactly what happened to it - just that it increased.

    If you knew the actual scores (not just ranges of scores) and knew that 85 was definitely the most common score, you'd know that the mode probably increased to 90 (since all of those 85's would have been increased to 90's). However, it doesn't sound like you know that, and, to make matters worse, since all scores are capped at 100, any score that used to be in the range of 96-100 would now become exactly 100. Therefore, there's a good chance that after increasing the scores, 100 would actually be the most common and therefore would be the new mode. But with only information about gross ranges of scores, you can't be sure of that either.

    So yes, I agree with all your conclusions. :)
  • Mar 30, 2011, 03:38 AM
    pop000
    Comment on jcaron2's post
    Thank you , you helped me a lot :)

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