binomial probab qu (1 Viewer)

[currysauce]

well 2 qu's

The probability of a brand of light globes being faulty is 1.3%. In a batch of 8 light globes, find the probab, as a % correct to 1 d.p that

a) none will be faulty
b) 6 will work
c) at least 7 will

when i do it i get some stupid number x10 ^23 LOL

 

[mojako]

probability that it's faulty = p = 0.013
probability that it works = q = 0.987

(a)
q⁸ = 90.1%

(b)
⁸C₆ p² q⁶ = 0.4%

(c)
P(7 will work) + P(8 will work)
= 8 p q⁷ + q⁸
= 99.6%