标题: normal distribution SD question [打印本页] 作者: ashycal 时间: 2013-4-2 11:38 标题: normal distribution SD question
on a practice problem I am having trouble with…the answer says 99% of observations fall w/in 3 SD of the mean. I had thought 99% of the observations fall w/in 2.575 SD of the mean…? Please someone clarify, it has been a very long day 作者: Mechanic 时间: 2013-4-2 11:38
that is what i memorized too!作者: Mechanic 时间: 2013-4-2 11:38
Turn to pg 326 in Volume 1 CFA book.作者: ramzes 时间: 2013-4-2 11:39
Thanks njlevel10610. how did the PM mock go for you?? I dont know if I was just tired or what, but it seemed harder than the AM?? Ethics in the PM were hard.作者: dece2011 时间: 2013-4-2 11:39
someone want to clarify this…dont have the book handy right now. Thanks作者: Finalnub 时间: 2013-4-2 11:39
there is a graph that says something like 99.7% of observations (for a norm dist) fall w/in + 3 SD of the mean…
it just confused me bc a lot of the quant questions refer to the use of 99% conf interval and + 2.575…
the .7% must be represented by the .425 SD difference …
hopefully that helped a little bit.作者: agulani 时间: 2013-4-2 11:40
I thought that was a garbage question, too. I’ve memorized 90/1.65, 95/1.96, 99/2.58 and that’s what I’m using on the exam.作者: btcapital 时间: 2013-4-2 11:40
pg441
The key word is “Approximately”:
Approximately 68% fall in +1SD
Approximately 95% fall in +2SD
Approximately 99% fall in +3SD
