The Student Room Group

Stuck on an easy Probability Question

22% of voters support the Conservatives, 30% Labour, 14% some other party, with 34% not supporting
a political party. When asked what party they support, voters either answer truthfully or
refuse to answer; the probability of a refusal is 25% for a Conservative supporter, 20% for a Labour
supporter, or 5% for everyone else.

(i) What proportion of voters say that they support the Conservatives?

Got an Answer = 0.165 = 16.5%

(ii) Of those who do answer, what proportion claim to be Conservative supporters?
Stuck Here
P(Conservatives|They answer) = 0.165/I don't know what goes here

(iii) Of those who refuse to answer, what proportion actually support a political party? [5 marks]
- No idea aswell

It is really weird how I can questions harder than this on different topics but this probability stuff, I just dont get

Thanks
MathsRus
Original post by mathsRus
22% of voters support the Conservatives, 30% Labour, 14% some other party, with 34% not supporting
a political party. When asked what party they support, voters either answer truthfully or
refuse to answer; the probability of a refusal is 25% for a Conservative supporter, 20% for a Labour
supporter, or 5% for everyone else.

(i) What proportion of voters say that they support the Conservatives?

Got an Answer = 0.165 = 16.5%

(ii) Of those who do answer, what proportion claim to be Conservative supporters?
Stuck Here
P(Conservatives|They answer) = 0.165/I don't know what goes here



If you can find the percentage who answer con then you can find the percentage that answer lab etc
Therefore you can find the percentage that answer
Original post by mathsRus
22% of voters support the Conservatives, 30% Labour, 14% some other party, with 34% not supporting
a political party. When asked what party they support, voters either answer truthfully or
refuse to answer; the probability of a refusal is 25% for a Conservative supporter, 20% for a Labour
supporter, or 5% for everyone else.


(iii) Of those who refuse to answer, what proportion actually support a political party? [5 marks]
- No idea aswell


If you could find the percentage that answered ... You can find the percentage that didn't
And you can find those who don't answer but support con or lab
Reply 3
Original post by TenOfThem
If you can find the percentage who answer con then you can find the percentage that answer lab etc
Therefore you can find the percentage that answer


Got it, you see I did not understand what it meant by answer. i.e. I thought it was
1-(Refused to answer)

ii) Ans = 19.16%

iii) Still working out

Thanks
Reply 4
Original post by TenOfThem
If you could find the percentage that answered ... You can find the percentage that didn't
And you can find those who don't answer but support con or lab


Could you check if the first answer is correct?

Now P(Didnt Answer) = 1 - 0.861 = 0.139

Is P(Support Party) = 0.22*0.75+0.3*0.8+0.14*0.95 = 0.538 = Correct?

Damn I am probably the weakest at probability stuff lol

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