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# Ocr mei statistics 1 exam thread (24/05/13) Watch

1. the question with water bottle and tap bottle
The last part was like 46 boxes find the expectation so i did 46 times the answer i got in my last question anyone did the same?
2. Did anyone else get like 14000 for the variance or something like that, 145541 i know it had 14 in the start and it was a big number, not sure if thats right but it did seem like a massive number.
3. For the last part of the last question, I got so confused. Was it saying probability of hitting 3 in 6 throws? But if she hits 3 in the first 3, she stops.....so P(B*B*B in first 3) + (If 1B in first 3, 2 in next 3) + (2B in first 3, 1 in next 3)..

e.g.
BBB
BNNBBN
NBNBBN

etc?
4. (Original post by Mahinder)
the question with water bottle and tap bottle
The last part was like 46 boxes find the expectation so i did 46 times the answer i got in my last question anyone did the same?
5. (Original post by juniorx)
oh **** looks like i made a mistake then
aaargh i just calculated it now and it is 5.62x10-3. I'm not sure and can't remember if it i put 5.62 or 5.82
6. (Original post by Blobar)
Did anyone else get like 14000 for the variance or something like that, 145541 i know it had 14 in the start and it was a big number, not sure if thats right but it did seem like a massive number.
I got that too! I wasn't sure if it was right....
7. (Original post by superxo2)
For the last part of the last question, I got so confused. Was it saying probability of hitting 3 in 6 throws? But if she hits 3 in the first 3, she stops.....so P(B*B*B in first 3) + (If 1B in first 3, 2 in next 3) + (2B in first 3, 1 in next 3)..

e.g.
BBB
BNNBBN
NBNBBN

etc?
Nope sorry thats wrong because it said if she hits one in the first 3 throws then she just stops

so

BBB NNNBBB
if it was BNNBBN she'd just stop after BNN
8. (Original post by Blobar)
yeh thats what i did
9. I almost did it wrong since I carried on from my 50 bags from the previous question so was doing P(X=0) 50C0 (0.9)^50, lucky I had time to go through all the question again and saw my mistake! Phew!
10. (Original post by Blobar)
Did anyone else get like 14000 for the variance or something like that, 145541 i know it had 14 in the start and it was a big number, not sure if thats right but it did seem like a massive number.
yesss i got a number that started with 1455... it was a big number!
11. how did u do your tree diagram and what did subsequently mean i think i got it all wrong haha
12. omfg i think i got the same as u for the var x
13. (Original post by Blobar)
Nope sorry thats wrong because it said if she hits one in the first 3 throws then she just stops

so

BBB NNNBBB
if it was BNNBBN she'd just stop after BNN
oh!! I misread the question !!
14. (Original post by Blobar)
Nope sorry thats wrong because it said if she hits one in the first 3 throws then she just stops

so

BBB NNNBBB
if it was BNNBBN she'd just stop after BNN
i nearly made that mistake and wasted 20 mins before i reread the question and actually understood it.
15. (Original post by superxo2)
oh!! I misread the question !!
Don't worry it was a toughie, when I first read it I wasnt even going to bother with it but I had like 20 minutes left lol so kinda forced myself into it.
16. (Original post by Attz_09)
how did u do your tree diagram and what did subsequently mean i think i got it all wrong haha
What mean? The questions were what is the probability she hits atleast one and what is the probability she gets exactly one.
17. someone plz remind me wtf question 3 was ?????
18. do you think the grade boundary will be lower or higher than jan 2013? it was 57/70 I think in Jan!
19. (Original post by tumblrgirl)
do you think the grade boundary will be lower or higher than jan 2013? it was 57/70 I think in Jan!
20. (Original post by Mahinder)
someone plz remind me wtf question 3 was ?????
the P(X=r) one I think. First question was mean and sd, 2nd one was the bags stuff, 3rd one envelope one and E(x) and var (x).

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