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#1 2006-12-02 10:04:16

freddogtgj
Member
Registered: 2006-12-02
Posts: 54

Probability

I really need some help in figuring out what type of distribution the following are

i)The number of games played by a football team up to and including its first win,
assuming that there is a probability 1/3 that it wins each game independent of results
in other games.

ii) The number of sixes occurring when 7 standard fair dice are rolled.

iii) The number of marks you score on a single question on an Essential Mathematical
Skills exam which you do not know the answer to.

iv) The total number of marks you score on an Essential Mathematical Skills exam if
you do not know the answer to any of the questions.

Plus, how would i work out the E(x) and Var(x)?
Thanks!!

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#2 2006-12-05 06:26:39

Stuart S
Member
Registered: 2006-12-05
Posts: 1

Re: Probability

i) Geometric

X~Geo(1/3)
E(X) = 1/(1/3) = 3

VAR(X) = q/(p^2) = (2/3)/(1/9) = 6

ii) Binomial
X~B(7, 1/6)
E(X)=7(1/6) = 7/6

VAR(X) = 7(1/6)(5/6) = 35/36

iii) Looks like it'll be a Binomial but more info is needed such as the number of marks but P would be 1/2

iv) Same as iii

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