A manufacturer produces ultra cheep light bulbs, in lots of 75, in which 12% of the bulbs are defective. An inspector selects a box and randomly selects 7 bulbs. What is the probability that no more than 2 of the 7 bulbs are defective?

Question

anonymous · Answer

my wild guess is 29/175 :P let me know if i am right i going to bed

anonymous · Answer

wrong :( i know the answer : 0.9664545
I just dont at all know how to go about finding it.

anonymous · Answer

aaa i have to give it another look at another time. I going to work :P

directrix · Answer

Probability of no more than 2 defects
Probability of a defective bulb = .12
Probability of good buld = .88
Binomial Probabilty
No more than 2 defects means 0 defects, 1 defect, or 2 defects
Zero Defects: C(7,0) (.12)^0 * (.88)^7
One Defect:   C (7.1) (.12)^1 * (.88)^6
Two Defects: C (7,2) (.12)^2 * (.88)^5
Probability of No More than Two Defects =
C(7,0) (.12)^0 * (.88)^7 + C (7.1) (.12)^1 * (.88)^6 + c (7,2) (.12)^2 * (.88)^5 =

directrix · Answer

= 0.9583611609088