MonkeyBusiness

someone....?

JRossSter

L(80) = (n+1)*(y/100) = (10+1)*(80/100) = 8.8.

Since L(80) is 8.8, you'd use interpolation:

P(80) = X(8) + [L(80) - 8]*[X(9) - X(8)] = 8 + (8.8 - 8)*(9 - 8) = 8.8.

Note that in this case L(80) = P(80) by mere coincidence - not always the case.

As mentioned earlier, refer to the example on page 376 L1V1R7. Good luck remembering the formula. Haha.



Edited 1 time(s). Last edit at Wednesday, May 11, 2011 at 11:11AM by Oyster.

bapswarrior

disiz64 Wrote:
-------------------------------------------------------
> Did someone find why the answer was the 8th
> largest number (on 10) for the 80th percentile??
>
> The CFAI Mock was incorrect?


I have written to CFA institute about it and they have forwarded it to their Education Department. Should hear back sometime soon. Will let you know what they say.

ftwcfa

Did someone find why the answer was the 8th largest number (on 10) for the 80th percentile??

The CFAI Mock was incorrect?

Benjiko

disiz64 Wrote:

> Ok. Thank you.


So I heard back. The question and the answer are correct. When you have a sample from a population and you need fourth quintile of the POPULATION, you use (n+1)y/100
In case you have the sample and you need to find the fourth quintile of the SAMPLE, you use ny/100 (that's what I understand)

dotamasta

Sorry but I dont understand what you really mean. Can you please repost their answer? I encouter the same difficulty in figuring out why they have that answer. Thanks

pogo

maxmeomeo Wrote:
-------------------------------------------------------
> Sorry but I dont understand what you really mean.
> Can you please repost their answer? I encouter the
> same difficulty in figuring out why they have that
> answer. Thanks


Max it's very easy..don't sweat!..it's the difference between "sample" and "population"..pay attention! Like in other areas as well such as standard deviation also treats sample and population differently by considering n-1 for sample and n for population so the same difference is here n+1 for population and n for sample..Makes sense?

dcfox83

Oh ok thank you Guess im too nervous to see thing properly

rkapoor

So I guess we have to pay attention to the wording of the question...

If population: n+1 * y/100
If sample: n*y/100

It would of been nice if this was clearer in the material studied...