Binomial Q

[kenhung123]

Having trouble with this question, not sure how to deal with 2 sets of info.
I was assuming its a conditional prob but gives wrong ans.

[the.watchman]

It's not a conditional question, the idea is that the entire batch has 90% satisfactory tyres

So let X be the number of satisfactory tyres
X can be represented by a binomial distribution with n=8 and p=0.9

So

(I'm lazy so I did it in my calc, but it's probably better to do it by hand )

[kenhung123]

I don't really understand the idea of the question. So practically, the guy is going to check all 8 tyres, if 6+ are OK he buys them...so how is there a Pr(X)?

[the.watchman]

I have Pr(he buys them)=Pr(Number of satisfactory tyres >0.75), right?
So incorporating the fact that the particular batch has 90% satisfactory tyres, then the solution is as above

[pooshwaltzer]

SEE PIC ATTCHMT

[the.watchman]

Lol, nice!