I have absolutely no idea how to do these.. any help?

I. The probability that two carriers of Cooley's anemia will have an afflicted child in any given birth is 0.25. If a carrier couple had five children, find the probability that:

1. At most two is afflicted
2. Exactly two are afflicted
3. At least two are affflicted
4. Find the mean
5. Find the standard deviation.

II. Night demand for, Y, for emergency room nurses has the following probability distributions:

Y| 0 1 2 3
P(Y)| 0.05 0.25 0.45 0.25

what is the probability of demand for @ least two?
what is the probability of demand for @ most one?
what is the probability of demand for none?
what is the mean demand?


If anyone can help explain these to me it would be greatly appreciated!

I. Let X be the random variable 'number of children afflicted with disease'. Assuming independence, X ~ Binomial(n = 5, p = 0.25).

II. Where are you stuck? It's a straightforward use of the table ....

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Thanks so much!

& on the second one, I just don't know how to use the table..

where you substitute the required probabilities from the given table.

etc.

And you should know that mean = (0) Pr(Y = 0) + (1) Pr(Y = 1) + (2) Pr(Y = 2) + (3) Pr(Y = 3) = ....

__________________
There are two things you should never try to prove: the impossible and the obvious.

The greater danger for most of us lies not in setting our aim too high and falling short; but in setting our aim too low and achieving our mark. (Michelangelo Buonarroti)

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