Poisson distribution

  • Thread starter pinto89a
  • Start date
  • #1
5
0
Nr of customers arriving at a shop follow Poisson.
In 15, an average of 4 customers arrive.

a)
A customer has just arrived. Then a minute passed and no one arrived. What is the probability of it takoing at least 5 more min. until another customer arrives?

b)
Consider 40 non-overlapping periods of 15 min.

What is the probability that
at least 7 and at most 15 of those intervals have at most 2 customers arriving?

In book, answer to
a) is 0.2636
b) is F(2.22) - F(-1.12) = 0.855

In a) although I don't see why, I understande that it's something about memorylessness or something. But how do you get to the answer in question b)?
 

Answers and Replies

  • #2
525
5
how do you get to the answer in question b)?
via binomial distribution
 
  • #3
5
0
Ok, I see now.Thank you.
 

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