1. ## Binomial probability

A poll shows that 70% of all voters approve of the mayor's work. On three separate occasions a pollster selects a voter at random. What is the probabilty that on exactly one of these three occasions the voter approves of the mayor's work?

Could someone please explain this as easy as possible?

Vicky.

Thanks.

2. Originally Posted by Vicky1997
A poll shows that 70% of all voters approve of the mayor's work. On three separate occasions a pollster selects a voter at random. What is the probabilty that on exactly one of these three occasions the voter approves of the mayor's work?

Could someone please explain this as easy as possible?

Vicky.

Thanks.
If X is the random variable 'number of voters who approve of the mayor' then X ~ Binomial(n = 3, p = 0.7). Calculate Pr(X = 1).

3. Originally Posted by mr fantastic
If X is the random variable 'number of voters who approve of the mayor' then X ~ Binomial(n = 3, p = 0.7). Calculate Pr(X = 1).

Thanks for your help. But I don't know what Binomial probability means.
But I could think of three cases

1st person 2nd person 3rd person

1 approve disapprove disapprove

2 disapprove approve disapprove

3 diapprove disapprove approve

Vicky.

4. Originally Posted by Vicky1997
Thanks for your help. But I don't know what Binomial probability means.
But I could think of three cases

1st person 2nd person 3rd person

1 approve disapprove disapprove

2 disapprove approve disapprove

3 diapprove disapprove approve

Vicky.

Calculate the probability of each outcome. Add the results. That's the answer.

5. Originally Posted by mr fantastic
Calculate the probability of each outcome. Add the results. That's the answer.
I think I got the answer.

7/10 X 3/10 X 3/10 = 63/1000

3/10 X 7/10 X 3/10 = 63/1000

3/10 X 3/10 X 7/10 = 63/1000

189/1000

Thanks!!!

6. Originally Posted by Vicky1997
I think I got the answer.

7/10 X 3/10 X 3/10 = 63/1000

3/10 X 7/10 X 3/10 = 63/1000

3/10 X 3/10 X 7/10 = 63/1000

189/1000

Thanks!!!
Correct. (And you're welcome).