Q9 Probability (2 Viewers)

[Timothy.Siu]

(a) It is estimated that 85% of students in Australia own a mobile phone.
(i) Two students are selected at random. What is the probability that neither 2
of them owns a mobile phone?

i think that the answer is <2.25%
but i just put 2.25%

 

[charlesdinio]

we got totally different answers

I wasnt sure whether to go:

15/100 x 15/100

OR

0.15 x 2

I think I ended up with 0.15 x 2.

Would like to know the answer also..

 

[walkahz]

its .15x.15

 

[lionking1191]

we got totally different answers

I wasnt sure whether to go:

15/100 x 15/100

OR

0.15 x 2

I think I ended up with 0.15 x 2.

Would like to know the answer also..

its just 0.15^2

isn't 0.15x2 0.3 ??

 

[charlesdinio]

yeah i dont know.

you both just said different things!

think about it literally.

if 85% of aus school kids have phones, 2 are selected, whats the chances they dont have phones,

if you do the old 0.15 x 0.15, 9/400 is a tad hard to believe

however, 3/10 is believeable?

I'm not sure to be honest.

 

[Kelly47]

I do general, and to me it sounds like it would be .15 X .15.
I dropped out of 2 unit though lol.
Because when you find the probability of events occuring in orders like that question, you times both probabilities together. But what would I know? I only do general lol.

 

[Timothy.Siu]

nah, but when u pick one, and he doesn't have a phone, then the next one you pick will have a lesser chance of having a phone.
e.g.

say there are 100,000 australian students
15% dont hav a phone so 15,000
picking 2 that dont hav a phone is 0.15x14999/99999=0.0024987....
there shouldn't be replacement

 

[2S1D3]

You have to multiply 15% *15%

 

[minijumbuk]

(15/100)^2

 

[Timothy.Siu]

yeah i dont know.

you both just said different things!

think about it literally.

if 85% of aus school kids have phones, 2 are selected, whats the chances they dont have phones,

if you do the old 0.15 x 0.15, 9/400 is a tad hard to believe

however, 3/10 is believeable?

I'm not sure to be honest.

why is it hard to believe, the probability becomes less if u want 2 that both dont have phones how can it be 3/10, thats greater than the probability of one student not having a phone, so you are saying that theres a greater chance of finding 2 students that dont have a phone, then the chance of finding one without a phone

 

[Timothy.Siu]

(15/100)^2

but after u pick one student without a phone the sample space becomes smaller,and with one of the people without the phone out of the sample space

THE QUESTION WAS WORTH 2 MARKS

 

[Kelly47]

nah, but when u pick one, and he doesn't have a phone, then the next one you pick will have a lesser chance of having a phone.
e.g.

say there are 100,000 australian students
15% dont hav a phone so 15,000
picking 2 that dont hav a phone is 0.15x14999/99999=0.0024987....
there shouldn't be replacement

This is the kind of question we get in general, and I believe this person is right. Say there were 100 people. The answer would be 15/100 x (I think) 14/99, and then whatever that equals lol. Honestly it sounds like a general question.

 

[Timothy.Siu]

hmm also, the question says "(a) It is estimated that 85% of students in Australia own a mobile phone."
it says estimated, so in your answer you should say approximately (your answer)

 

[erm]

but after u pick one student without a phone the sample space becomes smaller,and with one of the people without the phone out of the sample space

THE QUESTION WAS WORTH 2 MARKS

ur an idiot.

The sample space is so large that the events are considered independent NOT dependent. i.e. the probability of each event will not be affected by a previous outcome.

(as you have shown us the difference is quite small anyway)

 

[Timothy.Siu]

ur an idiot.

The sample space is so large that the events are considered independent NOT dependent. i.e. the probability of each event will not be affected by a previous outcome.

yeah thats wat i was thinking.

 

[M@ster P]

can someone explain why the answer is 01.5^2.

 

[Timothy.Siu]

can someone explain why the answer is 01.5^2.

theres a 15% chance u'll pick someone without a phone and in that 15% chance theres a 15% chance u'll pick another one without a phone
soo 15%x15%

 

[Smeegen999]

nah, but when u pick one, and he doesn't have a phone, then the next one you pick will have a lesser chance of having a phone.
e.g.

say there are 100,000 australian students
15% dont hav a phone so 15,000
picking 2 that dont hav a phone is 0.15x14999/99999=0.0024987....
there shouldn't be replacement

thats ridiculouss

 

[charlesdinio]

if i had the correct answer with the correct working and then drew a line through it and wrote the wrong answer, do you rekon they will give 1?

 

[Timothy.Siu]

if i had the correct answer with the correct working and then drew a line through it and wrote the wrong answer, do you rekon they will give 1?

maybe if they can read it