Qmb (1 Viewer)

[hongco1990]

Qmb pass

Hi all,
Im a bit lost in this exercise (from PASS Kevin-Fiona). Hope you guys will help me out with this. Ta.

Population is normally distributed. Standard deviation of 20mins. How large a sample if wanna achieve 90% confidence within 1min?

I know we gotta use the sample size formula, but does the difference in time (20mins and 1min) matter in this case?

 

[mr.nice.guy]

honestly, forget about that pass exserice, try starting the QMB project

 

[hongco1990]

lol, we gonna have in tut test nxt wk, and i dun wanna screw evrything out. I worked it out anyway

btw, I emailed Sasan yesterday about the project concern as my fckng Chinese tutor didnt know anything about project discussion which was designed in wk 7 tut. He said I could go to his/tutor in charge's consultation for help. So I think if you have any trouble with the instruction sheet itself, you should go and ask. Dont just wait until the last minute.

 

[runnable]

Do you have the answer?

(2(1.645 x20))/1 squared

to give 4329.64... 4330?

 

[mr.nice.guy]

lol, we gonna have in tut test nxt wk, and i dun wanna screw evrything out. I worked it out anyway

btw, I emailed Sasan yesterday about the project concern as my fckng Chinese tutor didnt know anything about project discussion which was designed in wk 7 tut. He said I could go to his/tutor in charge's consultation for help. So I think if you have any trouble with the instruction sheet itself, you should go and ask. Dont just wait until the last minute.

btw, wif our quiz 3 .. they say its topics from week 1 - 8, but would the topics be mostly from lectures 6-8? corz there ain't not much point quizing us the same shit again..
Btw whaat were the topics between weeks 6-8

 

[Arowana21]

(1.645*20)^2= 1082

 

[hongco1990]

@ mr.nice.guy: I think mostly based on wk 6-8 lec, which include normal distribution, converting binomial to normal distribution and hypothesis testing. Of course the knowledge covered in previous lecs from wk1-5 can be tested as well, but I think they wont test us directly on that.

@ runnable: I think Aronawa21's answer should be right. As in this week tut solution on Vista, they multiplied ((standard deviation * z alpha/2) / B) by 2 I think pretty much because the question is "the width is no more than 2 units". If in the question we are given "within 2 units", so we dont need to multiply by 2 at all. So the formula for this PASS question will be the same as in text book:
n = [(std deviation * z alpha/2) / B] squared

 

[mr.nice.guy]

@ mr.nice.guy: I think mostly based on wk 6-8 lec, which include normal distribution, converting binomial to normal distribution and hypothesis testing. Of course the knowledge covered in previous lecs from wk1-5 can be tested as well, but I think they wont test us directly on that.

@ runnable: I think Aronawa21's answer should be right. As in this week tut solution on Vista, they multiplied ((standard deviation * z alpha/2) / B) by 2 I think pretty much because the question is "the width is no more than 2 units". If in the question we are given "within 2 units", so we dont need to multiply by 2 at all. So the formula for this PASS question will be the same as in text book:
n = [(std deviation * z alpha/2) / B] squared

tanks

 

[mr.nice.guy]

Re: Qmb pass

Hi all,
Im a bit lost in this exercise (from PASS Kevin-Fiona). Hope you guys will help me out with this. Ta.

Population is normally distributed. Standard deviation of 20mins. How large a sample if wanna achieve 90% confidence within 1min?

I know we gotta use the sample size formula, but does the difference in time (20mins and 1min) matter in this case?

yo i got a question as well:
week 8 pass nick and nick and james :
In a certain community, 60% of the residents are in favour of building a new library. A random sample of 200 ppl is taken. Find the probability that 100 or less of these ppl favour the construction of the library.

Ans: 0.0025

 

[chewy123]

Re: Qmb pass

I don't think the answer is correct. 0.0025 is wayyy to small when you think about it.

Presumably the question is about correctional factors. The mean is just 200x0.6=120
The standard deviation is root npq. that is, root(200x0.6x0.4) which gives 48.
Then use standard transformation NOTE X=99.5 NOT 100 due to correction stuff.
P(z<-0.427) = 0.5 - 0.1628= 0.3372

Methink that's the answer, but i could be wrong.....

 

[runnable]

Re: Qmb pass

chewy: npq gives variance, not s.d so the s.d is actually root 48

I got the ans to be 0.0025 with X=100.5, not 99.5

 

[whoisurdaddy]

hmm why is X 100.5 not 99.5 btw?

 

[runnable]

The conversion is

X< or equal to 100
so X < 100.5 in normal approximation.

 

[chewy123]

+1 runnable

sigh sigh, i screwed my qmb test so severely, sigh sigh~~

 

[runnable]

Same... my questions were worded strangely..

 

[whoisurdaddy]

A lot of people got questions with 2 different samples, have we even learnt this?!

 

[melaniestrollll]

idk have we?

 

[whoisurdaddy]

dw its all good we have learnt it.