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# Edexcel s1 June 2016 unofficial mark scheme

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1. (Original post by KevinClyde;[url="tel:65800621")
65800621[/url]]You were told they were independent so P(AnB)= P(A) x P(B) then rearrange. I almost forgot to add the value at the bottom of the circle, maybe you did that?
Holy crap 😊

I think I got 63-65/75, just hoping it's a mid-high A :/
3. (Original post by tripleseven)

I think I got 63-65/75, just hoping it's a mid-high A :/
I'd say pretty standard, if anything slightly lower boundaries.
4. (Original post by veldt127)
Well, E(x) is the sum of x over n, right?

E(1/x) is the sum of 1/x over n.

(p(X = x)( (Σ1/x) )/n is not the same as (p(X = x)(1/( (Σx)/n ))
To maybe simplify this explanation with an example, the gist of the reason is that Σ(1/x) is not equal to 1/(Σx).

For instance, take two values: x = 2 and x = 3.
1/(Σx) = 1/(2+3) = 1/5
Σ(1/x) = 1/2 + 1/3 = 5/6
So the two are completely different.
5. Can someone pls post model answers with how many marks each question was?
6. (Original post by ShatnersBassoon)
To maybe simplify this explanation with an example, the gist of the reason is that Σ(1/x) is not equal to 1/(Σx).

For instance, take two values: x = 2 and x = 3.
1/(Σx) = 1/(2+3) = 1/5
Σ(1/x) = 1/2 + 1/3 = 5/6
So the two are completely different.
Thanks, I was struggling to get that across without huge amounts of brackets
7. (Original post by Jackhawkins21)
3c> was -131.9 and 5 Cii> was 0.689
I got this too
8. (Original post by ShatnersBassoon)
The question was 3 marks. In the worst case, no, you'd get 0/3 (1 mark for saying it's a bad model; another for saying mean =/= median; a third for comparing d to the actual answer).

You didn't compare your answer to part (d) to anything, but the question explicitly told you to, so you've definitely lost a mark there. I'd give you 1/3 but maybe if they're generous you'd get 2/3.
Thanks
9. Looks like some threads were merged together. Whoever is now the OP, can you make a poll with number of marks people think they got? helps with predicting. glad-he-ate-her
70 - 75
65-70
60-65
55-60
50-55
45-50
40-45
less than 40
10. (Original post by veldt127)
Ok, I managed to get all my answers stored in my calculator at the end, this is what I got. Not 100% sure on all of them, but we can compare.

Question 1
Spoiler:
Show
a. Show that
b. W - can't remember reasoning
c. 0.994
d. 0.0772 + 0.0142d
e. i. 5.69
ii. Reliable as the data was interpolated; it was within the range
Question 2
Spoiler:
Show
a. 2p + q = 0.5
b. q = 0.15
c. p = 0.175
d. 2.12
e. 0.45
f. i. 0.475
ii. 0.375
Question 3
Spoiler:
Show
a. 2.35
b. Show that
c. -133.9 - possibly -131.9
d. -0.754
e. Increase - I tried using the variables from the new week and recalculating r, and it was higher than the original. I said because the values were both higher than the means; I'm not sure at all on this one.
Question 4
Spoiler:
Show
a. 0
b. t = 0.03
c. u = 0.22
d. i. 0.45
ii. 15/37
e. 33 people have dinner (40*0.18) + (37*(15/37))
Question 5
Spoiler:
Show
a. Width 0.5, Height 17
b. 3.47 (median)
c. i. Show that
ii. Standard deviation = 0.680 - possibly 0.689
d. P(W<3) = 0.2546
e. No - the mean is not equal to the median suggesting asymmetrical skew18% of babies were less than 3kg, but her model predicted 25.46%
f. i. Mean remains the same as the new value is the mean
ii. The standard deviation decreases as the variance decreases with a new value close to the mean
Question 6
Spoiler:
Show
a. 0.0668
b. 206 - The lowest 20% of times were the fastest 20% of runners.
c. 0.36
What was 2.35 for?
11. Mate there was a VERY similar question in one of the past papers, fortunately did it the night before hahah - You just had to subtract the value they gave from 1 to get 0.18, and "P(X<u)" is just the mean, and the mean represents 0.5 in a normal distribution model; therefore 0.18/0.5 = 0.36.
12. (Original post by WreckTangle14)
Im super super confused with question 6c, i had NO idea it completely threw me off, could anyone explain?
Mate there was a VERY similar question in one of the past papers, fortunately did it the night before hahah - You just had to subtract the value they gave from 1 to get 0.18, and "P(X<u)" is just the mean, and the mean represents 0.5 in a normal distribution model; therefore 0.18/0.5 = 0.36.
13. (Original post by veldt127)
Ok, I managed to get all my answers stored in my calculator at the end, this is what I got. Not 100% sure on all of them, but we can compare.

Question 1
Spoiler:
Show
a. Show that
b. W - can't remember reasoning
c. 0.994
d. 0.0772 + 0.0142d
e. i. 5.69
ii. Reliable as the data was interpolated; it was within the range
Question 2
Spoiler:
Show
a. 2p + q = 0.5
b. q = 0.15
c. p = 0.175
d. 2.12
e. 0.45
f. i. 0.475
ii. 0.375
Question 3
Spoiler:
Show
a. 2.35
b. Show that
c. -133.9 - possibly -131.9
d. -0.754
e. Increase - I tried using the variables from the new week and recalculating r, and it was higher than the original. I said because the values were both higher than the means; I'm not sure at all on this one.
Question 4
Spoiler:
Show
a. 0
b. t = 0.03
c. u = 0.22
d. i. 0.45
ii. 15/37
e. 33 people have dinner (40*0.18) + (37*(15/37))
Question 5
Spoiler:
Show
a. Width 0.5, Height 17
b. 3.47 (median)
c. i. Show that
ii. Standard deviation = 0.680 - possibly 0.689
d. P(W<3) = 0.2546
e. No - the mean is not equal to the median suggesting asymmetrical skew18% of babies were less than 3kg, but her model predicted 25.46%
f. i. Mean remains the same as the new value is the mean
ii. The standard deviation decreases as the variance decreases with a new value close to the mean
Question 6
Spoiler:
Show
a. 0.0668
b. 206 - The lowest 20% of times were the fastest 20% of runners.
c. 0.36
please can you tell me how you worked out Q2 f i and ii ? like the general ideas of going about it ? thank you
14. (Original post by logicmaryam)
I'm pretty sure I got it wrong haha but ill add your answer and others' so people can discuss it.
This is the definition of standard deviation : a quantity expressing by how much the members of a group differ from the mean value for the group.

Therefore if there is another value in the data and it is the same as the mean, overall the data should be less weighted away from the mean.

I might be wrong but..
15. (Original post by tripleseven)

I think I got 63-65/75, just hoping it's a mid-high A :/
Considering how easy the paper was...

72 - A
70 - B
12 - C
8 - D

etc etc, you get the pattern
This is the definition of standard deviation : a quantity expressing by how much the members of a group differ from the mean value for the group.

Therefore if there is another value in the data and it is the same as the mean, overall the data should be less weighted away from the mean.

I might be wrong but..
odds are
1.0.994
w=0.721 + 0.0142d
5.691 response was wiggle
2.p=0.175 q=0.15
varx=2.115
E (r) was 0.45 rebecca and sarah winning 0.475 0.375
3. 2.35 -133.9 -0.754
4.0 0.03 0.22 0.45 0.405 33 was number of diners
5. K=0.5
h=17
med=3.47
0.68
0.2546
6. 0.0668
206.336
0.36

Feel free to correct or give answers to non numerical questions
18. (Original post by bobbutitii)
odds are
unfortunately the odds are always against me
unfortunately the odds are always against me
cool story bro, you'll get used to it.
20. (Original post by bobbutitii)
cool story bro, you'll get used to it.
NEVER, what did you write

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