SOLUTION: the probability that a double glazing salesperson will make a sale on a particular day is 0.05. what is the probability that over a three day period the sale person will make: 3 sa

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Question 1011016: the probability that a double glazing salesperson will make a sale on a particular day is 0.05. what is the probability that over a three day period the sale person will make: 3 sales, exactly 1 sale, at least 1 sale?
Answer by mathmate(429) About Me  (Show Source):
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Question:
the probability that a double glazing salesperson will make a sale on a particular day is 0.05. what is the probability that over a three day period the sale person will make: 3 sales, exactly 1 sale, at least 1 sale?

Solution:
We note that the questions satisfies the requirements of the binomial distribution, namely, known number of trials (n=3), constant probability (p=0.05), trials (days) are independent.
We need to assume that the salesman can only make a maximum of one sale a day.
The probability of making x sales in three days is given by the binomial distribution:
P%28X=x%29=C%28n%2Cx%29%2Ap%5E%28x%29%2Aq%5E%28n-x%29
Where C(n,x) is the combination function where C(n,x)=n!/(x!(n-x)!)

A. Probability of making 3 sales in three days, P(X=3)
P%28X=3%29=C%283%2C3%29%2A0.05%5E3%2A%280.95%29%5E0=0.000125

B. Probibility of making exactly one sale
P%28X=1%29=C%283%2C1%29%2A0.05%5E1%2A%280.95%29%5E2=0.13538

C. Probability of making at least one sale
P%28X%3E=1%29+=+1-P%28X=0%29+=+1-C%283%2C0%29%2A0.05%5E0%2A0.95%5E%283%29+=+0.14263