ECMT quiz 2 (3 Viewers)

[sarevok]

For 3b), I got a standard deviation of 1307 and a mean of 3673. Can any one confirm this? I dunno, the stdev seems kinda big.

 

[ToO LaZy ^*]

me: 1 stas: 0
poobrains.

 

[stazi]

sarevok can you go through each line of working?

 

[absolution*]

For 3b), I got a standard deviation of 1307 and a mean of 3673. Can any one confirm this? I dunno, the stdev seems kinda big.

that seems correct

 

[sarevok]

zzzzzzzzzzzzzzzzzzzz

 

[ToO LaZy ^*]

zzzzzzzzzzzzzzzzzzzz

saverok...you always seem to be sleepy
why is that the case?..attending murray's lecture yeah?

 

[matt#1]

saverok...you always seem to be sleepy
why is that the case?..attending murray's lecture yeah?

I think he does that when he wants people to post up more of their answers *hint*

 

[stazi]

zzzzzzzzzzzzzz

 

[sarevok]

zzzzzzzzzzzz

 

[stazi]

sorry i was a bit pissed off as I really needed to know how it's done.
Are you sure it's correct?
Z1 = -1.28
Zu = 1.98
Shouldn't z upper correspond to P(Z>zu)=0.03 and your lower one seems correct.

i.e.
P(X>2000) = 0.90
Thus, Z1=-1.28

P(X>6000)=0.03
Thus, Zu=1.88

Statistic:
Z=X - u / o

Equation 1:
-1.28 = 2000 - u / o
***-.128o+u = 2000
(not sure how you got this line, just a typo?. Should it be -1.28o + u = 2000?)

Equation 2:
1.88 = 6000 - u / o
1.88o + u = 6000

Ok, now as for solving simulatenously, why does multiplying by one cancel the u's? I get really lost there in the explanation. The line after it has completely baffled me. Where does all that come from?

 

[ToO LaZy ^*]

I think he does that when he wants people to post up more of their answers *hint*

*hint hint*

 

[sarevok]

zzzzzzzzzzzzzzzz

 

[ToO LaZy ^*]

on another note..someone said that 2b) was 1 and 99..can't remember who
that answer is incorrect i'm affraid.
the answer posted by absolution (pg 2) is the correct answer

 

[absolution*]

Maybe were both wrong in the same way toolazy?

 

[ToO LaZy ^*]

X ~ N(50,25) <-----------25 is the variance!..not the stdv.

 

[absolution*]

are you sure

i thought X ~ (mean, stdev)

 

[stazi]

i know i got some of 2 wrong.

 

[ToO LaZy ^*]

No he does that because he's a [.....] Other people are always sharing and trying to maximise their marks. Sarevok contributes when he needs help, and then promptly deletes any posts that he makes with anything that could be useful to us.

finally..someone who understands my sarcasm.

absolution: yeah, i'm 99% sure

 

[absolution*]

good
looks like i was right then

 

[ToO LaZy ^*]

I did in this way:
P(X>2000)=0.9
P(X>6000)=.03
In the other words:
P(X<2000)=0.1
P(X<6000)=0.97
Then
1:2000-u/SD=2.33(Z value from normal table)
2:6000-u/SD=1.88(As above)

Slove 1 and 2, I got u=4213.78; SD=950.12
Any commente?

i got the same answer