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# Edexcel S2 - 27th June 2016 AM watch

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1. (Original post by NotNotBatman)
No, , it wouldn't really matter in continuous distribution, but just stick to less than or equal.
Thankyou!
2. (Original post by fpmaniac)
If you do poisson for any question, the probability you find from that, is that always a fixed probability.
Sorry! Just saw this now, I think notifications are messed up. And yes it is in S2 so you are able to the same with any other situation given !
3. would I get penalised for integrating with respect to x instead of t when working out the cdf?
4. Please can someone explain question 1b https://57a324a1a586c5508d2813730734...%20Edexcel.pdf Thanks
5. (Original post by daviid1562)
would I get penalised for integrating with respect to x instead of t when working out the cdf?
They probs wouldn't care if you use x but might as well use some other variable just to avoid confusion, otherwise you're treating x as both a variable and a particular fixed value
6. (Original post by 13 1 20 8 42)
They probs wouldn't care if you use x but might as well use some other variable just to avoid confusion, otherwise you're treating x as both a variable and a particular fixed value
Thanks. I just got used to writing it with respect to x from the beginning
7. (Original post by daviid1562)
Thanks. I just got used to writing it with respect to x from the beginning
One way is just make one of the xs capital and one of the xs small as it's less change
8. Pleas e someone help me 😭
I've posted this four times
Question:
6aii

I don't understand why we are looking at the upper critical value and not the lower critical value as it says minimum

Attachment 556929

MS: Attachment 556931

Posted from TSR Mobile
9. (Original post by Music With Rocks)
Yeah you can be asked to work out the variance through integration (for uniform distribution) , which is basically the proof
Oh right thank you!
10. (Original post by economicss)
Please can someone explain question 1b https://57a324a1a586c5508d2813730734...%20Edexcel.pdf Thanks
Hi just done that question so thought i'd chip in!

Because its in 48 hours lambda become (1.6)

since that period greater than or equal to 1 cars are caught you work out the probability of 1-P(X=0) to find the probability

hope that helped sorry i have no idea how to do the symbols!
11. (Original post by Bloom77)
Pleas e someone help me 😭
I've posted this four times
Question:
6aii

I don't understand why we are looking at the upper critical value and not the lower critical value as it says minimum

Attachment 556929

MS: Attachment 556931

Posted from TSR Mobile
Your question is more to do with 6ai rather than 6aii, but as they are in parts..

the test above is testing solely whether lambda (the rate of visits or whatever) should be greater, so there is no need to look in the lower region because we're not testing whether lambda is actually smaller (it is a one sided test, basically).

The 'minimum' is just the minimum value in the critical region found as a result, which is 11. You could have 20 visotors or 40 or even 60000 (theoretically, but very, very, slim). but the minimum (the first value) where the hypothesis is rejected is when X=11. anything less than 10 and you keep the original lambda, so it is insignificant.
12. https://57a324a1a586c5508d2813730734...%20Edexcel.pdf

June 2006 question 7
why is it binomial distribution?
13. If anyone feels **** about tomorrow, just remember I started revision an hour ago

14. Just to clarify, the MODE is the X value that gives the highest Y value, right? So you give the x coordinate not the y coordinate?
15. (Original post by iMacJack)
Just to clarify, the MODE is the X value that gives the highest Y value, right? So you give the x coordinate not the y coordinate?
Yes in the pdf
16. can someone check june 2006 question 7a and tell me why it is a binomial and not a poisson?>
17. (Original post by Ellie_k98)
Hi just done that question so thought i'd chip in!

Because its in 48 hours lambda become (1.6)

since that period greater than or equal to 1 cars are caught you work out the probability of 1-P(X=0) to find the probability

hope that helped sorry i have no idea how to do the symbols!
Thanks so much! I don't suppose you could help me with question 4f here please https://57a324a1a586c5508d2813730734...%20Edexcel.pdf The mark scheme says it is symmetrical and so P(1<x<2)= 11/36 also but I don't understand why! Thanks
18. (Original post by economicss)
Thanks so much! I don't suppose you could help me with question 4f here please https://57a324a1a586c5508d2813730734...%20Edexcel.pdf The mark scheme says it is symmetrical and so P(1<x<2)= 11/36 also but I don't understand why! Thanks
It's a quadratic graph so it's symmetrical about it's minimum/maximum. Since 2 is the middle, and you're given the area between 2 and 3, it must be the same as between 1 and 2
19. (Original post by Abc321zxc)
can someone check june 2006 question 7a and tell me why it is a binomial and not a poisson?>
You're told that 1 in 5 bowls are defective. That implies that the probability of a bowl being defective is 0.2.
20. (Original post by Abc321zxc)
can someone check june 2006 question 7a and tell me why it is a binomial and not a poisson?>

A binomial distribution usually implies a cap. Whereas with Poisson, like measuring rate of customers, theoretically there is no cap on the number of customers that could come in a period of time. The binomial for example is different, because if you're tossing 20 coins it is impossible to get 25 or 30 heads, something that a poisson distribution would imply.

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