Asked by Raj

X follows normal distribution(400,64).Find the inter-quartile range of the distribution.

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asked by Raj
today at 2:24am
There are 16 pieces of data in each quartile. The inter-quartile range is
Q3 - Q1

How to find Q3-Q1?And is n=sd/4?
Answered by Ms Pi 3.14159265358979323
To find Q3 you need to look up .75 on your z-score table. You will see that the number associated with that is .674 so that means that to be in the 75th percentile (Q3) you must be 0.674 standard deviations above the mean value.
The mean is 400 so... 400 + (.674x64) = 443.13
while
Q1 would be 0.674 standard deviations below the mean (since the normal distribution is symetrical)
Q1 = 400- (.674 x 64) = 356.87
Now you need Q3 - Q1 : )
Answered by Raj
The answer is 10.784.So different from your calculations.
Answered by Ms Pi 3.14159265358979323
Hmmm... let me check some numbers...
Answered by Raj
There was another part of the question too which I did myself finding the limits within which the central 95% of the distribution lies.
Answered by Ms Pi 3.14159265358979323
LOL! (mean,sigma^2)
so the standard deviation is 8 thus
with 0.674 above and below...
gives my answer to be 10 even...
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