SOLUTION: from past records, a store finds that 26% of people who enter the store will make a purchase. 18 people enter the store during 1-hour period a) what is the probability that exactl

Question 1064696: from past records, a store finds that 26% of people who enter the store will make a purchase. 18 people enter the store during 1-hour period
a) what is the probability that exactly 10 customers make a purchase? 18 customers? 3 customers?
b) find the expected number of customers who make a purchase.
c) find the variance and standard deviation of the number of customers who make a purchase

Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
The parameter of this Poisson distribution is 4.68, 26% of 18. Discrete, proportional to time, can be theoretically infinite.
For 10:
e^(-4.68)*4.68^10/10!
=0.0129. The mean and variance would be expected to be 4.68, and the sd the sqrt (4.68), or 2.16
--------------------
e^(-4.68)(4.68^18)/18!=1.68 x 10^(-6)---For 18
-------------------
For 3:
e^(-4.68)*4.68^3/3!=0.1585
The expected value is 4.68 customers.
The variance is the same as the expected value and the sd 2.16
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