SOLUTION: Best Electronics Inc. Offers a "no hassle" return policy. The daily number of customers returning items follows the normal distribution. The mean number of customers returning item

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Question 1150922: Best Electronics Inc. Offers a "no hassle" return policy. The daily number of customers returning items follows the normal distribution. The mean number of customers returning items is 10.3 per day and the standard deviation is 2.25 per day.
a. For any day, what is the probability that eight or fewer customers returned items?
b. For any day, what is the probability that the number of customers returning items is between 12 and 14?
c. Is there any chance of a day with no customer returns?
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!
a. In what percent of the days are there 8 or fewer customers returning items?

z%288%29+=+%288-10.3%29%2F2.25+=+-1.0222
%(x%3C=8 )= %(z%3C=-1.0222) = 15.33%

b. In what percent of the days are between 12 and 14 customers returning items?
Normalcdf%2812%2C14%2C10.3%2C2.25%29 = 17.49%

c. Is there any chance of a day with no returns?
z%280%29+=+%280-10.3%29%2F2.25 = -4.5778
%(x%3C=0+)= %(z%3C=-4.5778) = 0.00023518%