ECMT quiz 2 (1 Viewer)

[stazi]

Ok have done question 1. My tablet pen thingo is poop. Bought it today and it absolutely sucks. you can't use it properly. So I can't really write up extended stuff.

For the first one, all we can do is approximate. You will notice that the latger the Z value, the smaller the difference is.

 

[absolution*]

Hmmm.

I think 1 a) is a misprint/typo. 4.2 st dev from mean is silly.

Do qu 3 stas you big homo

 

[sarevok]

any one know how much of the standard normal table we get given in exams? iirc tig said we'd only get the one for positive Z's

 

[absolution*]

I also think 2 d) is a typo. Me thinks tig was tapping some a-grade yankee ass when he was typing it up.

 

[absolution*]

any one know how much of the standard normal table we get given in exams? iirc tig said we'd only get the one for positive Z's

Negative Z's are the exact opposite of positive Zs, theres no need for both.

We recieve the full Z (0.00-3.49) im quite sure.

 

[stazi]

Hmmm.

I think 1 a) is a misprint/typo. 4.2 st dev from mean is silly.

Do qu 3 stas you big homo

Why can't it be 4.2 stdev from the mean? The table in the back of the book goes to 6STDEV from the mean.


Don't mind me. I am re-taaaraded. Was doing sampling distribution instead of normal dist on Q2

 

[absolution*]

<3 ecmt.

 

[stazi]

Edit: this is serious. my brain literally has stopped thinking constructively. I suffered a pretty bad head injury yesterday. I'm going to go rest.
ah poop. my brain isnt working.
can someone tell me how they got 2.a.

c=µ+Zσ

c=50+0.95(25)
=73.75

I'm getting this and it seems wrong. I'm not standardising the values.

 

[stazi]

Oh wait.

Is it just z=1.64
c=50+1.64(25)
c=91
I think it works out if you reverse the formula as well.

Z=c-m/stdev
=(91-50)/25
Z=1.64
=0.9495 (closest one to 0.95)

So, P(Z<1.64) = 0.95 (aprox) = P(X<91) = 0.95 (aprox)

Which one of us is wrong?

 

[absolution*]

If i could be bothered getting my working i would. But i have gas.




Im pretty sure im wrong though. Very sure. Ive never done these sorts of problems before.

 

[spin spin sugar]

hi!!!!!!!!!!

 

[sarevok]

stdev of 5? the stdev is 25, right?

anyway, i got a difference answer for 2a) (bet i did something really stupid)

Zc = 1.645

Z = (C - MEAN)/STDEV
C=Z*STDEV+MEAN
C=1.645*25+50 = 91.125

edit: 1.645 because it's the average of 1.64 and 1.65, and the average of the probs of those two is 0.95 exact

 

[absolution*]

oh noes. its grace in an ecmt thread. call tha authoritiezzzzzzz

 

[absolution*]

stdev of 5? the stdev is 25, right?

anyway, i got a difference answer for 2a) (bet i did something really stupid)

Zc = 1.645

Z = (C - MEAN)/STDEV
C=Z*STDEV+MEAN
C=1.645*25+50 = 91.125

edit: 1.645 because it's the average of 1.64 and 1.65, and the average of the probs of those two is 0.95 exact

yeah i wrote the thing as (50,5) on my sheet coz my printer is whory so i had to write the questions out.

im a bigdumbass.

 

[absolution*]

edit: 1.645 because it's the average of 1.64 and 1.65, and the average of the probs of those two is 0.95 exact

Ok. This is one thing i dont understand and ties in with above.

If on the table the number you want is between two other numbers, what do you do, providing its not able to be averaged like sarevok has done.

Ie. You want 0.913

And the closest two values on the table are.. 0.911 and 0.919

 

[sarevok]

Just take the one that's closer, I guess

Any one got any ideas for q3b? This question's really annoying, I've never seen a question like it before and I have no idea how to do it >=|

 

[Rorix]

its in last weeks lecture notes under proportion

 

[stazi]

stdev of 5? the stdev is 25, right?

anyway, i got a difference answer for 2a) (bet i did something really stupid)

Zc = 1.645

Z = (C - MEAN)/STDEV
C=Z*STDEV+MEAN
C=1.645*25+50 = 91.125

edit: 1.645 because it's the average of 1.64 and 1.65, and the average of the probs of those two is 0.95 exact

Yep, i think that is pretty much correct. I just took 1.64 and you took 1.65.

Poop, i fell asleep. Head traumas arent homoerotic.

Grace. You're poo.

 

[ToO LaZy ^*]

omg..is teh answers!!1.

*aroused*

i would do some qs to help us out...but ..er..my foot hurts

 

[stazi]

And question 2. Absolution, you got many different results to me. Can everyone also check if theyre correct. Same with Q1. We must all get 100UAI in this quiz.

Furthermore, could someone explain q3.a.
My logic is a bit off.

How do we find the probability of him arriving after 8:30, based on him leaving at 8:00?
I understand if it was just P(X>8:30)
Although, I'm not even sure if that would be correct as minutes an hours only have 60 and 24 units. This could lead to incorrect calculations.