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

1. (Original post by 4nonymous)
round and chose the closest one
Yea that's what I usually do, but for the June 2013 (R) paper, question 4b, they needed the value of z for a probability of 0.85. I used 1.04, as it had a probability closest to 0.85, but the mark scheme used 1.0364.
2. LOOOOOL june 13 r wasn't even that hard why is everyone complaining about it? i got 70/75 and finished it in 30 mins
3. (Original post by Haamoo7)
Yea that's what I usually do, but for the June 2013 (R) paper, question 4b, they needed the value of z for a probability of 0.85. I used 1.04, as it had a probability closest to 0.85, but the mark scheme used 1.0364.
you used the wrong sign hence you used z< instead of z> which requires percentage points
4. (Original post by tazza ma razza)
you used the wrong sign hence you used z< instead of z> which requires percentage points
Oh okay. I see where I went wrong now.

Thanks
5. Can anyone help with this?

I was doing this past paper:
https://1a388b28f5ce9318f837a64962fc...%20Edexcel.pdf

and their reasoning for question 3d is very strange. Would I have gotten the marks if I had used 3(mean-median)/SD ?

Thanks guys!
6. (Original post by tazza ma razza)
LOOOOOL june 13 r wasn't even that hard why is everyone complaining about it? i got 70/75 and finished it in 30 mins
Alright big guns!

Some questions were a bit different, e.g. for 3D I hadn't seen that reasoning before and I did 3(mean-median)/SD so I'm not sure if I'd have gotten the marks or not.
7. (Original post by tazza ma razza)
you used the wrong sign hence you used z< instead of z> which requires percentage points
Quick question though. Using the method I did, it wasn't technically wrong. I reversed the inequality direction and made the probability 1 - the original probability, it's just that I did it to an insufficient accuracy.

The answer to that question was 14.5, and I got 14.4.

Would I still get the method marks and lose that 1 accuracy mark for the answer?
8. (Original post by tazza ma razza)
LOOOOOL june 13 r wasn't even that hard why is everyone complaining about it? i got 70/75 and finished it in 30 mins
Don't lie, you can't have finished a stats paper in less than 30 minutes, even if you got 70/75!
9. (Original post by thelegend99)
Can anyone help with this?

I was doing this past paper:
https://1a388b28f5ce9318f837a64962fc...%20Edexcel.pdf

and their reasoning for question 3d is very strange. Would I have gotten the marks if I had used 3(mean-median)/SD ?

Thanks guys!
mean > median >mode => postive skew
im not sure about your method cus i dont usually use it, only if the question gives you the formula, but the mark scheme allows it for alt so it wont be the case
10. (Original post by thelegend99)
Can anyone help with this?

I was doing this past paper:
https://1a388b28f5ce9318f837a64962fc...%20Edexcel.pdf

and their reasoning for question 3d is very strange. Would I have gotten the marks if I had used 3(mean-median)/SD ?

Thanks guys!
Yes, any way of proving it's a positive skew is valid. The mark scheme are using: IF
Mean<Median<Mode-- Negative skew
Mean=Median=Mode-- Symmetrical (no skew)
Mean>Median>Mode-- Positive skew
11. (Original post by thelegend99)
Alright big guns!

Some questions were a bit different, e.g. for 3D I hadn't seen that reasoning before and I did 3(mean-median)/SD so I'm not sure if I'd have gotten the marks or not.
what you didn't know about mean<median = negative skew ?

besides, it will tell you if you need to use this, otherwise learn page 67 of the textbook
12. (Original post by tazza ma razza)
LOOOOOL june 13 r wasn't even that hard why is everyone complaining about it? i got 70/75 and finished it in 30 mins
Thank you for speaking on behalf of all of us m8. You deserve a peace prize and two cookies.
13. With normal distribution, when you have to standardize, do you have to look up the z value for 0.1 or can you just use it?

for example, P(X<200) = 0.1 (mean= unknown and SD= 7.8)
14. (Original post by Imperion)
Thank you for speaking on behalf of all of us m8. You deserve a peace prize and two cookies.
compared to the other papers, it is easy. Try june 10 (80 ums was 55/75 compared to 60 for june 13r)
15. When working out percentiles in continuous data do you multiply percentile/100 by n+1? and if so why?
16. I don't know what else I can do to revise at this point
17. (Original post by tazza ma razza)
compared to the other papers, it is easy. Try june 10 (80 ums was 55/75 compared to 60 for june 13r)
74 and 71 respectively for those papers and it wasn't easy. Js, what you find easy isn't what others will find the same. ATB for tomorrow!
18. Anyone have any ideas on the hardest questions you can get?
19. (Original post by asinghj)
I always do:
If they are independent then P(B|C) = P(B)
P(B) = 20/80 = 0.25
P(B|C) = (4+3)/28 = 0.25
Since P(B) = P(B|C) the events are independent
And that would get 3 marks for sure?
20. Guys, do you know where I could possibly get the June 2015 paper from?

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