SOLUTION: I am drawing a blank on how to even start solving. A shipment of 40 graphing calculators contain 8 defective units. A college bookstore buys 20 of these units. a. What is the

Algebra ->  Probability-and-statistics -> SOLUTION: I am drawing a blank on how to even start solving. A shipment of 40 graphing calculators contain 8 defective units. A college bookstore buys 20 of these units. a. What is the      Log On


   

Question 1021611: I am drawing a blank on how to even start solving.
A shipment of 40 graphing calculators contain 8 defective units. A college bookstore buys 20 of these units.
a. What is the probability of the bookstore receiving no defective units?
b. What is the probability of the bookstore receiving 2 defective units?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Your empirical probability of defective unit is 8%2F40=1%2F5.
Your empirical probability of non-defective unit is then 1-1%2F5=4%2F5.
Use the formula,
P%28X%29=C%2820%2CX%29%2A%281%2F5%29%5EX%2A%284%2F5%29%5E%2820-X%29
where X is the number of defective units.
a) No defective units X=0,
P%280%29=C%2820%2C0%29%2A%281%2F5%29%5E0%2A%284%2F5%29%5E%2820-0%29
P%280%29=%284%2F5%29%5E20
P%280%29=1099511627776%2F95367431640625
P%280%29=0.01153
b) 2 defective units, X=2,
P%282%29=C%2820%2C2%29%2A%281%2F5%29%5E2%2A%284%2F5%29%5E%2820-2%29
P%282%29=190%2A%281%2F25%29%2A%2868719476736%2F3814697265625%29
P%280%29=13056700579840%2F95367431640625
P%280%29=0.13691