Driving Test Passing Score Probability Questions

[Tina]

In one city, the probability that a person will pass his or her driving test on the first attempt is 0.67. 11 people are selected at random from among those taking their driving test for the first time. What is the probability that amont these 11 people, the number passing the test is between 2 and 4 inclusive?

A) 0.0353 B) 0.0365, C) 0.0408 or D) 0.0295.

I've come up w/bunches of figures and 3/11 and .67, etc. can't solve this. anyone able to conjure up a solution for me? i don't just want the answer. thanks a ton! tina

 

[tkhunny]

Simple Binomial Distribution Application.

Pr(0) = 1*(0.67^0)*(0.33^11)
Pr(1) = 11*(0.67^1)*(0.33^10)

Is this looking familiar? You do the rest?

 

[Tina]

Thank you tremendously for your reply. It doesn't look like, I mean, it appears the formula you've accustomed to use works, and it almost seems to me like more than one formula, or more than one way to get the answer? Not sure, but I selected B) for the answer and got it right, so thank you again.

 

[tkhunny]

You're serious? Please look up "Binomial Distribution". Actually read the material. You cannot have missed this formula. No book claiming to teach the Binomial Distribution ever would be published without out this formula.

 

[Tina]

It looks like this, and neither any student teachers at the community college in the tutoring section could help me. they said skip the problem.

P(x) = C(n,x)p^xq^n-x.

way too complicated. i need someone to SPEAK it to me. the online video didn't cover this - - may be its too complicated. i entered some of the questions to an online calculator and got answers. I guess, if i use it in real life, i'll have to figure it out, but for this class - - even the tutors i've spoken to "didn't really get into this stuff" so i'm told

believe me?

 

[tkhunny]

P(x) = C(n,x)p^xq^n-x.

That's exactly it! Good sleuthing.

n = 11
p = 0.67
q = 1-p = 0.33

C(n,x) = (n!)/(x!)((n-x)!)

Plug in n = 0 and n = 1 and just see if you don't get the two pieces I gave you before. Then you can complete the problem.

the online video didn't cover this - - even the tutors i've spoken to "didn't really get into this stuff" so i'm told

Yikes! I hesitate to tell you how inappropriate this situation is without knowing if you're stuck with it. Do you have ANY other situation available? I am not encouraged.