Probability question

[sasguru]

Rereading my notes on probability (I must be bored) I came across the following question:

One part of a quiz consists of 2 multiple-choice questions with the suggested answers
1. True
2. False
3. Insufficient Data to answer question.

A student randomly marks one of the 3 answers to each question.

What is the probability of exactly one correct answer?


Answers please with reasoning.

[oracleslave]

Rereading my notes on probability (I must be bored)

Why do the rest of us have to suffer?

[sasguru]

Why do the rest of us have to suffer?

Bit grumpy aren't we?
Didn't you have the requisite 30 bob in the red light district yesterday, then?

[Peoplesoft bloke]

Why do the rest of us have to suffer?

WHS

[TimberWolf]

1 in 9, since there are 3*3=9 combinations of answers: TT,TF,TI, FT,FF,FI, IT,IF,II

[sasguru]

1 in 9, since there are 3*3=9 combinations of answers: TT,TF,TI, FT,FF,FI, IT,IF,II

The actual answer is 4/9. But I can't work out why.
Your sample space is of course correct.

[oracleslave]

Bit grumpy aren't we?
Didn't you have the requisite 30 bob in the red light district yesterday, then?

Indeed, spent it all on beer .

There are 3 questions and the and the probability of success in each question is 0.3. So n = 3,p = 0.3.

The probability of x successes in n questions is nCx px qn–x where p and q are the probabilities of success and failure respectively.

Substitute n = 3, x = 1, p = 0.3 and q = 1 – p = 0.3 in the formula.
= 3C1 · (0.3)1 · (0.3)3 – 1


etc etc *


* I have no idea what any of this means, it is a straight copy from google

[ratewhore]

Fridays are dull enough without this sh1te...

[sasguru]

Indeed, spent it all on beer .

There are 3 questions and the and the probability of success in each question is 0.3. So n = 3,p = 0.3.

The probability of x successes in n questions is nCx px qn–x where p and q are the probabilities of success and failure respectively.

Substitute n = 3, x = 1, p = 0.3 and q = 1 – p = 0.3 in the formula.
= 3C1 · (0.3)1 · (0.3)3 – 1


etc etc *


* I have no idea what any of this means, it is a straight copy from google

Must have been good strong beer

[oracleslave]

Must have been good strong beer