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Twelve percent of the customers of a bank overdraw their accounts at least once a...

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PaulRosandro | eNoter

Posted September 6, 2013 at 8:15 AM via web

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Twelve percent of the customers of a bank overdraw their accounts at least once a month. A sample of eight customers is selected. What is the probability that exactly two customers in the sample will overdraw their account this month

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changchengliang | Elementary School Teacher | (Level 2) Adjunct Educator

Posted September 6, 2013 at 10:35 AM (Answer #1)

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Assumption: Company has a big customer base.

P(overdraw, once a month) = 0.12

P' = 1 - 0.12 = 0.88

P(Exactly 2 out of 8 customers overdraw)

= 1 - P(6 out of 8 customers did not over draw)

= 1 - 0.88^6

= 1 - 0.46440409...

= 0.53559591...

Approx.= 54%

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changchengliang | Elementary School Teacher | (Level 2) Adjunct Educator

Posted September 6, 2013 at 12:14 PM (Reply #1)

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Oops!  Ignore the previous answer.

Here is the correct one:

X is binomial distribution (n=8,p=0.12)  

P(X=2)

=8C2 .12^2  .88^6

=0.1872477...

= 18.7 %  (approx)

Sources:

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