# help me with this problem

• Dec 3rd 2007, 10:10 PM
arundathi
help me with this problem
• The time between calls to a plumbing supply business is exponentially distributed with a mean time between calls of 15 minutes.
(i) What is the probability that there are no calls within a 30 minute interval?
(ii) What is the probability that at least one call arrives within a 10 minute interval?
(iii) What is the probability that the first call arrives within 5 and 10 minutes after opening?
(iv) Determine the length of an interval of time such that the probability of at least one call in the interval is 0.90.

Thanks!
• Dec 4th 2007, 05:09 AM
colby2152
Quote:

Originally Posted by arundathi
• The time between calls to a plumbing supply business is exponentially distributed with a mean time between calls of 15 minutes.
(i) What is the probability that there are no calls within a 30 minute interval?
(ii) What is the probability that at least one call arrives within a 10 minute interval?
(iii) What is the probability that the first call arrives within 5 and 10 minutes after opening?
(iv) Determine the length of an interval of time such that the probability of at least one call in the interval is 0.90.

$F(0) = \frac{e^{-2}(2^0)}{2!}$
$= .0677$