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Standard deviation

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by ildude02 » Sun Sep 21, 2008 8:04 pm
My approach was, I got mean of 100 and then SD was 22.4 or 22. So, 1SD less than 100 was 78 and the question I thought was asking for how many times are more then 78, obvisouly I went wrong somewhere. Appreciate anyones response.
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by csandeepreddy » Sun Sep 21, 2008 8:26 pm
The question is asking for more than 1SD below the mean.

# below 78 from the sample set.

Is the answer 2?
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Re: Standard deviation

by justpal » Sun Sep 21, 2008 8:52 pm
The mean for the list of running times is
1000 / 10 = 100

SD = 22.4

Ques asks for how many running times are more that one SD below mean
that is 100-22.4 = 77.6

and we got 70 and 75 less than 77.6

Answer is TWO (B)
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Re: Standard deviation

by stop@800 » Mon Sep 22, 2008 7:50 am
ildude02 wrote:My approach was, I got mean of 100 and then SD was 22.4 or 22. So, 1SD less than 100 was 78 and the question I thought was asking for how many times are more then 78,
we need to find how many nos are below 17
its 2 ie 70 and 75
ildude02 wrote:
obvisouly I went wrong somewhere. Appreciate anyones response.
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