Post by: nerd on September 20, 2008, 05:32:55 pm
Question 1
I found the E(X) of a certain prob distribution to be 2.12, which is correct. It then asks me to find the Var(X) and sd(X). Firstly, are we excepted to be able to evaluate
Question 2
The hight of a certain population of adult males is normally districtuber with mean 174 cm and standard dev of 8 cm.
a) Find the probability that the height of a randomly selected individual will exceed 190 cm.
How do you do this without a calculator? ???
Post by: shinny on September 20, 2008, 05:55:49 pm
Post by: Collin Li on September 20, 2008, 06:02:17 pm
Question 1
I found the E(X) of a certain prob distribution to be 2.12, which is correct. It then asks me to find the Var(X) and sd(X). Firstly, are we excepted to be able to evaluateby hand? And even worse, how is one supposed to evaluate
for the standard dev? I CAN'T DO THAT WITHOUT A CALULATOR!!!
Weak.
Just kidding :P
Quote
Question 2
The hight of a certain population of adult males is normally districtuber with mean 174 cm and standard dev of 8 cm.
a) Find the probability that the height of a randomly selected individual will exceed 190 cm.
How do you do this without a calculator? ???
You can do this if you make some approximations. You know that two standard deviations from the mean is approximately 95% right? Use that fact. I'm not sure whether the course assumes that knowledge, or whether the exam paper will actually say something like: "you may assume that the probability of being within 2 standard deviations of the mean is 95%"
The answer should be 0.025
Post by: excal on September 20, 2008, 06:10:24 pm
Question 1
I found the E(X) of a certain prob distribution to be 2.12, which is correct. It then asks me to find the Var(X) and sd(X). Firstly, are we excepted to be able to evaluate
Weak.
Just kidding :PQuoteQuestion 2
The hight of a certain population of adult males is normally districtuber with mean 174 cm and standard dev of 8 cm.
a) Find the probability that the height of a randomly selected individual will exceed 190 cm.
How do you do this without a calculator? ???
You can do this if you make some approximations. You know that two standard deviations from the mean is approximately 95% right? Use that fact. I'm not sure whether the course assumes that knowledge, or whether the exam paper will actually say something like: "you may assume that the probability of being within 2 standard deviations of the mean is 95%"
The answer should be 0.025
Yes, they do. The 68% - 95% - 99.7% (empirical) rule I've seen in MM textbooks,
Post by: doboman on September 20, 2008, 06:12:26 pm
Post by: excal on September 20, 2008, 06:17:30 pm
Leave it in exact form.
Post by: Collin Li on September 20, 2008, 06:19:49 pm
Post by: Collin Li on September 20, 2008, 06:21:21 pm
Yes, they do. The 68% - 95% - 99.7% (empirical) rule I've seen in MM textbooks,
What do you mean by empirical? It's numerical, based from the formula the normal distribution is defined on. It's not evidence-based.
Post by: excal on September 20, 2008, 06:25:15 pm
Post by: Collin Li on September 20, 2008, 06:33:07 pm
Post by: /0 on September 20, 2008, 06:44:54 pm
Yes, they do. The 68% - 95% - 99.7% (empirical) rule I've seen in MM textbooks,
What do you mean by empirical? It's numerical, based from the formula the normal distribution is defined on. It's not evidence-based.
Isn't it true every time though? I mean, even for extreme cases of
Post by: Mao on September 20, 2008, 09:38:49 pm
but also keep in mind that it is only an estimate, and it is only accurate to the number of significant figures it has... so for that above case, it might be accurate to