A shipment of 12 microwave ovens contains 3 defective units. A vending company has ordered 4 of these units, and because all are packaged identically, the selection will be at random. What is the probability that at least 2 units are good?

Question

anonymous · Answer

so usually 1/4 of the shipment is defective. so if we get 4 units. and 1/4 is bad. then we hav 4*1/4 is bad. which gives you a grand total of 1 bad one.  so i think all the time you will have 2 good ones..

perl · Answer

no you re wrong

lgbasallote · Answer

are you classmates @perl & @EnchantixPixie ?

anonymous · Answer

No?

lgbasallote · Answer

:okay:

directrix · Answer

Probability of a defective oven = 3/12 = 1/4 = .25
Probability of a non-defective oven = .75

P( 2 Defects) = C(4,2) * (.25)^2 * (.75)^2 =  .2109
P( 3 Defects) = C(4,3) * (.25)^3 * (.75)^1  =  .0469
P(4 Defects) =  C(4,4) * (.25)^4 * (.75)^0 =  .0039
Probability of at least 2 defective ovens = .2109 + .0469 + .0039 = .2617