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# Edexcel S1 - 15th June, 2016 [Exam Discussion] watch

1. Ugh I answered the Sarah and Rebecca probability question a really long way around. Multiplimg all the possible options, if I'm incorrect do you think I could lose all 4 marks.
Prob Sarah wins :0.445 and Rebecca 0.46.... Something a,ing those lines.
2. (Original post by Raaj11)
Yeah same here, i said the exact thing. Not sure if its write thou
I think we are right for the mean but for the standard deviation, it would decrease because the new value was the same value as the mean therefore there is less deviation in the data set now.
3. (Original post by pranto96)
SD will not change! SD is root of sum of X - X bar divided by n. So as X- X bar is O is this case so sum of X-X bar do not change! so SD remains the same!
Yeah thats the same proof that i wrote s^2 sum(x-mean)^2 so yeah the sum - mean is zero. there for s doesnt change. I am not sure if its right thou
4. Exams are OVER!!!!!!!!!!!!
5. (Original post by uk_shahj)
I think we are right for the mean but for the standard deviation, it would decrease because the new value was the same value as the mean therefore there is less deviation in the data set now.
Yeah i figured out my mistake. The data would be less varied now so standard deviation would decrease.
I lost two marks for this question i guess?
6. (Original post by pranto96)
SD will not change! SD is root of sum of X - X bar divided by n. So as X- X bar is O is this case so sum of X-X bar do not change! so SD remains the same!
You're correct in saying that X - X bar stays the same, but n increases by one, so SD decreases.
7. I did the questions I was unsure on twice and didn't cross out anything and that seemed to be a good idea since all my second answers were correct haha.

Also what was 100UMS for last year's stats? This one felt a little harder so hopefully it's lower this year
8. I got 0.6 for the first Venn Diagram question, lol.
9. I got this too... But seems no one get this answer
10. I calculated Syy in a very complicated way by using the mean to find the sum of x, and the standard deviation to find the sum of x squared and then used the formula I know! Is this OK too for the 1 mark?

Never done a formula for Syy with mean and SD!
11. (Original post by Ae1in)
Ugh I answered the Sarah and Rebecca probability question a really long way around. Multiplimg all the possible options, if I'm incorrect do you think I could lose all 4 marks.
Prob Sarah wins :0.445 and Rebecca 0.46.... Something a,ing those lines.
I got this too but seems no one got the same answer
12. (Original post by logicmaryam)
Sorry haha, I messed up a few questions so it was much easier for me but I do think boundaries wont be lower than 60 for A
you are most likely an a2 resit, and you're not taking into consideration that the people who use student room are normal a/b grade students and you all forget about the countless numbers of people who will fail this and as there were no easy marks ( box plots) (draw venn diagram) in which people will pick all their marks up on. meaning boundaries will be significantly lower than last years by 2 marks give or take you found it easy because you're either retaking and have had 2 years of stats or you are naturally good at maths and will therefor be park of the a* boundary in which will not affect the other boundaries. so don't be so patronising for the other students by saying that the boundaries will be 64 for an A or definitely won't be sub 60 for an A.
13. (Original post by Raaj11)
Yeah i figured out my mistake. The data would be less varied now so standard deviation would decrease.
I lost two marks for this question i guess?
(Original post by ShatnersBassoon)
You're correct in saying that X - X bar stays the same, but n increases by one, so SD decreases.
I said the mean remains the same, but standard deviation is unchanged!

I didnt put any explanation dosn, do they need explanation for the marks? The question didnt say explain..
14. (Original post by themechguy)
I calculated Syy in a very complicated way by using the mean to find the sum of x, and the standard deviation to find the sum of x squared and then used the formula I know! Is this OK too for the 1 mark?

Never done a formula for Syy with mean and SD!
Do u know what u got for you Sxy and the pmrc ?
15. I know 0.1 and 0.2 is wrong for P and Q, but can someone tell how many marks I'll lose, cause my working for the rest of q was all right, just used the wrong numbers
16. (Original post by themechguy)
I said the mean remains the same, but standard deviation is unchanged!

I didnt put any explanation dosn, do they need explanation for the marks? The question didnt say explain..
I think they said give a reason for it, so i am assuming you have to explain something.
17. (Original post by hbaig27)
I know 0.1 and 0.2 is wrong for P and Q, but can someone tell how many marks I'll lose, cause my working for the rest of q was all right, just used the wrong numbers
will get all the method marks but loose all the A1 marks and some B1 maybe, so you would get about 50% of the marks, that is usually the case.
18. (Original post by Megan3245)
Exams are OVER!!!!!!!!!!!!
Lucky still got 6 exams left !!!!

you are most likely an a2 resit, and you're not taking into consideration that the people who use student room are normal a/b grade students and you all forget about the countless numbers of people who will fail this and as there were no easy marks ( box plots) (draw venn diagram) in which people will pick all their marks up on. meaning boundaries will be significantly lower than last years by 2 marks give or take you found it easy because you're either retaking and have had 2 years of stats or you are naturally good at maths and will therefor be park of the a* boundary in which will not affect the other boundaries. so don't be so patronising for the other students by saying that the boundaries will be 64 for an A or definitely won't be sub 60 for an A.
Lol, someones angry . Getting vexed quick.
19. VOTE HERE ON HOW YOU FOUND THE EXAM

http://www.thestudentroom.co.uk/show...1#post65795491
20. (Original post by Ae1in)
Ugh I answered the Sarah and Rebecca probability question a really long way around. Multiplimg all the possible options, if I'm incorrect do you think I could lose all 4 marks.
Prob Sarah wins :0.445 and Rebecca 0.46.... Something a,ing those lines.
same

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