Probibility question

Kenshinofkin · 2008-07-31 20:48:26

A pediatric nurse is studying the number of babies born at a hospital with congenial defects. Data shows that on the average, one baby with a congenial defect is born per month
a) What type of probability distribution is appropriate for this problem?
b) Find the expected number of babies born in one year with congenial defects.
c) Find the standard deviation of the number of babies born in one year with congenial defects.
d) Find the probability that no babies are born with congenial defects in one year.
e) Find the probability that at least one baby is born with congenial defects in a year.
f) Find the probability that exactly 12 babies are born with congenial defects in a year.

Only one I think I know is b) 12?

mathsyperson · 2008-08-01 01:23:14

That looks to me like a job for the Poisson distribution.
If you look that up on wikipedia, you could probably do the rest by yourself.

Post again if you need more help.

Kenshinofkin · 2008-08-01 02:06:39

I am not sure I am using this right but here goes.

d) f(k;lamda) = (0^12 * e^-0) /12! = 0
e) f(k;lamda) = (1^12 * e^-1) /12! = .8 x 10^9
f) f(k;lamda) = (12^12 * e^-12) /12! = .1114

Did I do this right?

mathsyperson · 2008-08-01 05:14:15

You're nearly right.

In the Poisson distribution formula, λ is the parameter that the distribution uses (which in this case is 12, regardless of what questions you are being asked) and k is the one you change.

So because the original formula is:

That would mean for d), you'd use

.

e) is basically asking you the probability that d) doesn't happen, so take the d) answer away from 1.

You've done f) right, except that when I do it I get an answer of 0.114...
You probably just made a typo though.

Kenshinofkin · 2008-08-01 05:52:32

Thank you so much!!!:D

Math Is Fun Forum

#1 2008-07-31 20:48:26

Probibility question

#2 2008-08-01 01:23:14

Re: Probibility question

#3 2008-08-01 02:06:39

Re: Probibility question

#4 2008-08-01 05:14:15

Re: Probibility question

#5 2008-08-01 05:52:32

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