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May 7th, 2009, 01:46 AM   #1
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find expected value, standard deviation, and probability

this is a homework help. I'm stumped as to which formula or chapter to look at. please show guidance. IM NOT ASKING FOR AN ANSWER, just guidance.

Q4. In a Gallup poll, 47% of the eligible women responding said that they would date a coworker. Suppose 350 employed women were selected at random.
a) What would be the expected value and standard deviation of the number of these women who would date a coworker?
b) What is the probability that at least 180 of them would date a coworker?

a) u = n*p = 380*0.47 = 178.6
s = square root ( n*p*q) = square root ( 380*0.47*0.53) = 9.7232

b) the "at least" is throwing me off. I have no idea how to start this.
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