Question 821282: Mimi just started her tennis class three weeks ago. On average, she is able to return 15% of her opponent’s serves. If her opponent serves 10 times, please answer the following questions:
Find the probability that she returns at most 2 of the 10 serves from her opponent.
How many serves is she expected to return?
.15*10= 1.5, or we can round up to say that she’s expected to return 2 of the 10 serves. <--- is that correct? And if so, doesn't that answer the above problem in a backwards way?
I can't figure out how to approach the first problem, and I attempted the second. Can you tell me how to work on the first problem and if I'm on the right track with the second one?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Mimi just started her tennis class three weeks ago. On average, she is able to return 15% of her opponent’s serves. If her opponent serves 10 times, please answer the following questions:
Find the probability that she returns at most 2 of the 10 serves from her opponent.
Binomial Problem with n= 10 and p(return) = 0.15
P(0<= x <=2) = binomcdf(10,0.15,2) = 0.8202
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How many serves is she expected to return?
u = np = 0.15*10= 1.5
Comment on your question: The 1st question asks for a probability.
The 2nd question asks for a count. The answer is 1.5, not 2.
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Cheers,
Stan H.
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