In article <[EMAIL PROTECTED]> in
sci.stat.edu, Eric Bohlman <[EMAIL PROTECTED]> wrote:
>Stan Brown <[EMAIL PROTECTED]> wrote in
>news:[EMAIL PROTECTED]:
>
>> The empirical rule tells you that _about_ 2.5% of the data will lie
>> above z = 2 in a normal distribution, not that _exactly_ 2.5% will
>> lie above. The smaller the population, the less closely it will
>> approach an ideal normal distribution and therefore the less good
>> that empirical rule will be. For 500 students the approximation
>> should not be too bad, _if_ the underlying distribution is
>> normal.(*) So your calculation correctly tells you that _about_ 12.5
>> students will have scores over 83. You would simply state this as
>> about 12 or 13 students.
>
>Another way to put it is that the OP's original distribution is discrete,
>but he's approximating it with a continuous distribution, and the area
>under the appropriate part of the curve of a continuous distribution
>doesn't have to evenly divide that of a discrete one.
I started to write that at first, but I don't think it's true. The
scores on the test may very well be continuous.
--
Stan Brown, Oak Road Systems, Cortland County, New York, USA
http://OakRoadSystems.com/
It's not necessary to send me a copy of anything you post
publicly, but if you do please identify it explicitly to avoid
confusion.
.
.
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