Question 1160659: III. Ten percent of computer parts produced by a certain supplier are defective. A sample of 10 parts was selected randomly. The computer parts produced are independent.
a) What is the probability that the sample contains exactly 3 defective ones?
b) What is the probability that the sample contains at most 2 defective ones?
c) What is the probability that the sample contains at least 3 defective ones?
d) What is the expected number and standard deviation of the defective computer parts produced?
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! exactly 3 are defective is 10C3*0.9^7*0.1^3=0.0574
at most 2 is p(0,1,2)
p=0.9298 from binomcdf(10,.1,2)
each of those is 0.3486, 0.3874 and 0.1937 respectively
at least 3 defective items is 1-at most 2, since those are complementary, and that is 1-0.9289=0.0702
E(X)=10*0.1=1 defective part
Var(X)=1*0.9 (np(1-p)0=0.9
sd is sqrt (V)=0.9487 or about 0.95 parts
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