The Student Room Group
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>

Edexcel S2 - 27th June 2016 AM

Scroll to see replies

Original post by SeanFM
Yeah.. your working is right.

But probability of being longer than 1mm I make to be 0.602.


Hmm.

P(X > 1) = 1 - P(X =< 1)

= 1 - [ P(X = 1) + P(X = 0) ]
= 1 - [ 0.425 + 0 ]

?
Reply 441
Avatar for SSD07
SSD07
3
Original post by NotNotBatman
The perimeter is 20cm, so the sum of the two sides is half the perimeter, which is 10cm. so x+y =10, consider the end points x=1; when x=1 x+y=10, so y=9.

When X=7, y=3, so it adds up to 10. so 1<x<7 and 3<y<9

Now either x or y can be the longer side, depending on their length. You're looking for the longer side to be more than 6cm, so that's when x>6 and y>6. When is y>6 when x<... (remember x+y=10). Then add the probabilities.

--------------------------
Or think about it like this 1<X<7, so 3<Y<9,

X~U[1,7] and Y~U[3,9], then work out the probabilities of both being greater than 6.


makes sense now! thank you so much
Does anyone know why p(x>1) is 1-F(1) because isnt it that p(x<1) = F(1)
Original post by economicss


Please can someone help :smile:
Original post by Aliceeee12
Does anyone know why p(x>1) is 1-F(1) because isnt it that p(x<1) = F(1)


p(x=1)=0 since continuous so p(x>1) = 1 - p(x<1) = 1 -F(1)
Original post by Mattematics
Hmm.

P(X > 1) = 1 - P(X =< 1)

= 1 - [ P(X = 1) + P(X = 0) ]
= 1 - [ 0.425 + 0 ]

?


I make the CDF to be (23x - 3x^2 )/40 - (49/480)
Original post by apzoe
I mean that the mark scheme says less than 4, while I was thinking it should be less than or equal to 4.

So that P(X>196) = P(Y<=4) (not = P(Y<4))


Because 'more' does not mean 'more and equal to', it just means 'more'.
Original post by MaxWalker1
p(x=1)=0 since continuous so p(x>1) = 1 - p(x<1) = 1 -F(1)


Thankyou! So if it is p(x>2) is that 1-F(2) or 1-F(1)
Original post by Aliceeee12
Does anyone know why p(x>1) is 1-F(1) because isnt it that p(x<1) = F(1)


F(1)=P(x≤1) F(1) = P(x\leq 1)

P(x>1)=1−P(x≤1)=1−F(1) P(x>1) = 1 - P(x\leq 1) = 1-F(1)
Original post by NotNotBatman
F(1)=P(x≤1) F(1) = P(x\leq 1)

P(x>1)=1−P(x≤1)=1−F(1) P(x>1) = 1 - P(x\leq 1) = 1-F(1)


Isnt the formula p(x<1) = F(1) instead of less than equal?
Original post by Aliceeee12
Thankyou! So if it is p(x>2) is that 1-F(2) or 1-F(1)


p(x>2) = 1 - F(2) for '''continuous''' data
Reply 451
Avatar for ktbunny
ktbunny
Original post by NoahMal
the answer is 1 Because it is continuous and much like a normal distribution the probability of a single number is 0 therefore the probability that it does equal that number is 0 so then 1-0 = 1.


thank you so much! i am so bad at this general knowledge about how distributions work, but i now understand more :thumbsup:
Original post by MaxWalker1
p(x>2) = 1 - F(2) for '''continuous''' data

Much appreciated tyy
Reply 453
Avatar for taysc
taysc
2
Original post by iMacJack
This is the probability it survives for less than t days


I'm really sorry I still don't understand
Original post by apzoe
I mean that the mark scheme says less than 4, while I was thinking it should be less than or equal to 4.

So that P(X>196) = P(Y<=4) (not = P(Y<4))


If 197 DO turn up, then 3 haven't turned up (198, 199, 200). Therefore you're looking for P(Y =< 3) which is P(Y < 4)
Reply 455
Avatar for SSD07
SSD07
3
Original post by Ayman!
Conditional probability applied to continuous distributions. Quite common as of late in stats papers - came up in my S3


do you know any S2 papers where this comes up? / Have any questions on it, just so i can practice some questions
started this on friday evening, didnt know what binomial was and now just got 65 on gold paper 4. two all nighters in a row sure work miracles lool
Original post by Aliceeee12
Isnt the formula p(x<1) = F(1) instead of less than equal?


No, F(x)=P(X≤x) F(x) =P(X\leq x), it wouldn't really matter in continuous distribution, but just stick to less than or equal.
Original post by SSD07
do you know any S2 papers where this comes up? / Have any questions on it, just so i can practice some questions


On S2? I've only done S2 papers since Jan 13 and it came up twice - IAL June 15 and Jan 13
Reply 459
Avatar for apzoe
apzoe
2
Original post by Mattematics
If 197 DO turn up, then 3 haven't turned up (198, 199, 200). Therefore you're looking for P(Y =< 3) which is P(Y < 4)


Oh I see now. Always mess up questions where you have to change the random variable.

So, for example, P(>=197) = P(X<=3). Thank you! Thank you Nikhilm as well!

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you