Asked by Sarah

A study of birds in California found 120 hummingbirds, 40 robins, 30 warblers, and 10 mockingbirds.

a) If a bird is randomly chosen from this study, what is the probability that it will be a hummingbird?

b) If a bird is randomly chosen from this study, what is the probability that it will be a robin or mockingbird?

c) If two birds are randomly chosen from this study, what is the probability that one will be a robin and the other will be mockingbird?

I tired these problems on my own and the answers I got were: a) 0.60 b) 0.25 and c) 0.25 but I am not sure if these are right.
Answered by oobleck
(a) and (b) are ok, but
(c) is
2 * 40/200 * 10/199
that is P(robin,mocker) + P(mocker,robin)
Answered by Sarah
(d) If an bird is randomly chosen from the population and then returned to the population (total number of birds is the same for all trials), what is the probability that we will select a hummingbird, then a mockingbird, and then a warbler?

how would I go about doing this?
Answered by oobleck
since each draw is taken from the total population of 200 birds, that would be
120/200 * 10/200 * 30/200
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