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# S2 poisson questions watch

1. Hi,

I don't understand how to answer these questions on poisson

If X~Po(10) find (a) P(X<=12) (b)P(X=9) (c)P(x>=7)

done those...

(ii) Two successive values of X are now chosen independently from the distribution. Find the probability that just one of them is at least 7.

________________________________ ___________________

In a country the mean number of deaths per year from lightening strike is 2.2. In a neighboring country, it is found that one year in 20 nobody dies from lightening strike. What is the mean number of deaths per year in the neighboring country.

The answer is 3. How do I get this?

________________________________ ____________________

350 raisins are put into a mixture which is well stirred and made into 100 small buns. Estimate how many of these buns will (i) be without raisins (ii)contain five or more raisins

Done this

(iii) In a second batch of buns, exactly one has no raisins in it. Estimate the total number of raisins in the second mixture.

Not sure how to do this?

Help needed. thank you.
2. anyone!?!
3. (Original post by math help)
Hi,

I don't understand how to answer these questions on poisson

If X~Po(10) find (a) P(X<=12) (b)P(X=9) (c)P(x>=7)

done those...

(ii) Two successive values of X are now chosen independently from the distribution. Find the probability that just one of them is at least 7.
If one is at least 7, then it is 7 or more. If just one is at least 7, the other must be less than 7.

So, either the first is less than 7, and the second is >= 7, or the first is >=7 and the second is < 7.

Can you finish that first one from there?

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