Proability

[sasa]

Help with prob qs? I can't remember ow to do this....simultaneous eqns?

[SocialRhubarb]

Mean of a binomial distribution is np.

Variance of a binomial distribution is np(1-p).

Additionally, p is a probability so cannot be greater than 1.

[shadows]

You can use two formulas


These formulas are for binomial distributions only

Mean (expected value) = np

Variance = np(1-p)

therefore for sd, you need to square root np(1-p)

then solve simultaneously to get your values of n and p.


haha beaten.. xD

[sasa]

So then I can figure it out simultaneously ....gahhhh!!!!

[sasa]

Done and done
Grrrr, why would I forget so,etching like that (and I didn't have it in my notes....whoops :/)

[Phy124]

Done and done
Grrrr, why would I forget so,etching like that (and I didn't have it in my notes....whoops :/)

Better to learn it now than after the exam

[sasa]

True, but I have my prob sac tomorrow. 

Seriously considering pulling an all-nighter ( I don't recommend it to others)  Zzzzzz

[clıppy]

Just a quick question in terms of notation, do we have to write that B~(mu, var) stuff, or can we just write, mu =, var(B) =?

[BubbleWrapMan]

Just a quick question in terms of notation, do we have to write that B~(mu, var) stuff, or can we just write, mu =, var(B) =?

For a multiple-choice question, you don't have to write anything.

For a written question, I guess it depends how many marks are available, but you should indicate to the examiners that you understand what all the parameters are and such. So yes, you should write out the distributions.

[TrueTears]

Just a quick question in terms of notation, do we have to write that B~(mu, var) stuff, or can we just write, mu =, var(B) =?

The conventional notation (at least in mathematical statistics and econometrics) is if is binomial random variable, then , with parameters and .