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Stats, probability

  1. Oct 13, 2005 #1
    1 out of 5 italians speak english. 1 out of 5 people in italy are tourists. 1 out 2 tourists speaks english.

    You meet a english-speaking person in italy, what is the probability that this person is italian.

    The way I see the "population":

    [itex]P(I) = \frac{2}{10}[/itex] are italians who speaks english.

    [itex]P(T) = \frac{1}{10}[/itex] are tourists that speaks english.

    You have meet someone from P(I) + P(T), what is the probability that this person is italian?

    That probability equates to:
    2x + 1y = 1 (x => english-speaking italian, y => english speaking tourist)

    Where do I go from here?
  2. jcsd
  3. Oct 13, 2005 #2


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    Science Advisor

    Your P(I) is wrong. It should be 4/5(italians) x 1/5 (speak English).
    Net result P(I)=.16, P(T)=.1.
    P(E) (english speaking)=.26. Your answer is P(I)/P(E).
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