Statistics question wtf (2 Viewers)

[Shadowdude]

its econ 1203 - BES/Statistics/Something

a lot of probability/numbers/interpreting graphs etc



and i love reporting goodwin for a ban 10 minutes after he signs up ahhhahhhahhhh

ECON1203? Hmm, that's a Commerce core isn't it?

 

[b00m]

correct, although economics and some other courses(?) also seem to do it as their core

 

[b00m]

Q8) Helen the auditor one.

I'm not terribly sure unless I read up fully.

But it appears to be:



where 1.28 is z-value for 20% significance (80% confidence )

That means whatever her estimate is, there is an 80% probability it is in the interval



Answer: 12.8 not guaranteed correct.

and ye this turned out to be incorrect
its alright though i somehow got 9/10 thnks for the halp gais

 

[Fighting4LastPl]

lol stats quiz

 

[cutemouse]

How can I calculate this if a standardised normal random variable (Z) of -8 isn't included in the cumulative standardised normal probabilities table in the appendix of my book.

What the fuck.

Use the Taylor series expansion.... (joke -- You'd require like 30 terms for 4dp accuracy)

 

[study-freak]

Q8) Helen the auditor one.

I'm not terribly sure unless I read up fully.

But it appears to be:



where 1.28 is z-value for 20% significance (80% confidence )

That means whatever her estimate is, there is an 80% probability it is in the interval



Answer: 12.8 not guaranteed correct.

You need to use 0.1 quantile of the standard normal distribution because the confidence interval is two sided.
And I think "margin of error"=half of confidence interval length? in which case we wouldn't have times two in the front. Depends on the definition.

 

[study-freak]

Let X denote the outstanding balances of customers of a firm. From past experiences X is well aproximated by a normal distribution with mean 45 and variance 100. If an auditor takes a random sample of 36 accounts what is the probability that the mean balance will be less than 45? (Your answer should be correct to one decimal place.)

gais, howd u do this one?^ or if not, where do i find the theory in the book.. im lagging by like 4 chapters lol ._.

mean balance~N(45,100/36) approximately by the Central Limit Theorem.
Note that the mean does not change and therefore the answer is simply 0.5 by symmetry of the normal density function about the mean.

 

[cutemouse]

And I think "margin of error"=half of confidence interval length? in which case we wouldn't have times two in the front. Depends on the definition.

Yeah if CI = [x bar +/- z_{1-alpha/2} rho/sqrt(n)]

then the margin of error m = z_{1-alpha/2} rho\sqrt{n}

ie. CI = [x bar +/- m]

(or whatever respective estimator you want)