SOLUTION: a salesman has a 20% probability of making a sale to any customer who enters his department. non a typical day, he will meet 30 customers. what minimum number of sales will he have

Question 1176709: a salesman has a 20% probability of making a sale to any customer who enters his department. non a typical day, he will meet 30 customers. what minimum number of sales will he have an 88% certainly of making for any given day.
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
binomial with n=30 and p=0.2
Expected mean is 6
expected variance is 4.8 (6*0.8)
expected sd is sqrt (V) or 2.19
p(0 sales) is 0.8^30=0.0012
p(1)=0.8^29*0.2*30=0.0093
p(2)=0.8^28*0.2^2*30C2=0.0337
p(3)=0.8^27*0.2^3*30C3=0.0785
p(4) from calculator is 0.1325
It would be 3 with a probability the sum of the first four, which is 0.1227

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