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by zorro
Wed Jul 07, 2010 2:06 am
Forum: Statistics
Topic: Let X, Y, be ind. Poisson rand. vars; mean 1; find P(X+Y=4),
Replies: 7
Views: 6946

Re: Let X, Y, be ind. Poisson rand. vars; mean 1; find P(X+Y

I couldnt understand how to evaluate P(A+B=4) as is it P(A+B=4) = P(A) + P(B) = 4 or is it some other way If X is poisson 1 and Y is poisson 1 then X+Y is Poisson 2 but how should i represent it in my solution P(A+B) = 1+1 = 2 but what about the '4' I am having a hard time how to formulate this ? s...
by zorro
Tue Jul 06, 2010 2:53 am
Forum: Statistics
Topic: Need to know which formulae which has been used
Replies: 2
Views: 3918

Re: Need to know which formulae which has been used

maggiemagnet wrote:If you're not sure what formula this is, try working backwards from the "sample" formulas they've given you. Which one uses in the numerator? Which one also uses in the denominator? :thumb:

Thanks!!
by zorro
Tue Jul 06, 2010 2:50 am
Forum: Statistics
Topic: Let X, Y, be ind. Poisson rand. vars; mean 1; find P(X+Y=4),
Replies: 7
Views: 6946

Re: Let X, Y, be ind. Poisson rand. vars; mean 1; find P(X+Y

Start with this... http://en.wikipedia.org/wiki/Poisson_distribution#Properties Thanks so \mu = \lambda = 1 P(A+B=4) = ? stuck here !!! From the link I provided look at "Sums of Poisson-distributed random variables" I couldnt understand how to evaluate P(A+B=4) as is it P(A+B=4) = P(A) + ...
by zorro
Mon Jul 05, 2010 4:04 pm
Forum: Statistics
Topic: Let X, Y, be ind. Poisson rand. vars; mean 1; find P(X+Y=4),
Replies: 7
Views: 6946

Re: Let X, Y, be ind. Poisson rand. vars; mean 1; find P(X+Y

Martingale wrote:
zorro wrote:Question :
Suppose X and Y are independent Poisson random variable , each with the mean 1 , obtain
i) P(X+Y=4)
ii) E[(X+Y)2]


Start with this...http://en.wikipedia.org/wiki/Poisson_distribution#Properties

Thanks

so = = 1

P(A+B=4) = ? stuck here !!!
by zorro
Mon Jul 05, 2010 11:41 am
Forum: Statistics
Topic: Let X, Y, be ind. Poisson rand. vars; mean 1; find P(X+Y=4),
Replies: 7
Views: 6946

Let X, Y, be ind. Poisson rand. vars; mean 1; find P(X+Y=4),

Question :
Suppose X and Y are independent Poisson random variable , each with the mean 1 , obtain
i) P(X+Y=4)
ii) E[(X+Y)2]
by zorro
Mon Jul 05, 2010 3:44 am
Forum: Statistics
Topic: prob. of 3 red, 2 white, 1 blue (is the answer correct)
Replies: 5
Views: 4711

Re:

stapel_eliz wrote:Assuming the decimal points stand for multiplication, could you please show the steps in your arithmetic with the fractions?


Sorry silly mistakes ....
P(R).P(R).P(R) + P(W).P(W) + P(B) = 0.4289
by zorro
Sun Jul 04, 2010 4:08 pm
Forum: Statistics
Topic: What is the probability that he really knows the answer
Replies: 4
Views: 4618

Re: What is the probability that he really knows the answer

Martingale wrote:
jk22 wrote:then p(knows|correct)=p(correct|knows)*p(knows)/p(correct)
=1*1/2*1/(p(correct|knows)p(knows)+p(correct|guess)p(guess)+p(correct|copy)p(copy))
=.5*1/(p(knows)+p(guess)+1/48)
=24/41


That number seems a little low.


If u know the answer can u please let me know ?
by zorro
Sun Jul 04, 2010 4:03 pm
Forum: Statistics
Topic: random var. X is -1, 0, 1 w/ equal probability (check ans)
Replies: 4
Views: 5039

Re: random var. X is -1, 0, 1 w/ equal probability (check an

Martingale wrote:
zorro wrote:Please can u tell what is wrong


My work ........
E(X) = 0

1 = 0

2= 2/3

2 = 2/3

var(X) = 2 - 2 = 2/3 - 2/3 = 0





Thanks !!! :clap:
by zorro
Sun Jul 04, 2010 4:00 pm
Forum: Statistics
Topic: prob. of 3 red, 2 white, 1 blue (is the answer correct)
Replies: 5
Views: 4711

Re: prob. of 3 red, 2 white, 1 blue (is the answer correct)

Martingale wrote:12 is not a probability


Could u please help me solve this problem by pointing out the mistake
by zorro
Sun Jul 04, 2010 10:27 am
Forum: Statistics
Topic: prob. of 3 red, 2 white, 1 blue (is the answer correct)
Replies: 5
Views: 4711

prob. of 3 red, 2 white, 1 blue (is the answer correct)

Question : A box contains 5 red balls, 4 white balls and 3 blue balls . A ball is selected at random from the box . the colour of the ball is noted and then replaced back . Find the probability that out of 6 balls selected in this manner , 3 are red, 2 are white , 1 is blue. Solution : Let P(R) be t...

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