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Arsey's S1 Edexcel Answers 18th Jan 2013

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Finally managed to start a thread....

Q1. Standard correlation. I think the mark scheme will be very generous in part c)

Q2. DRV. Pretty easy if you revised cumulative distribution questions.

Q3. Regression. Fairly easy as it was obvious that t was x.

Q4. Normal distribution. Standard apart from c) I think that will cause a lot of problems.
I think part c) is very badly worded.

Q5. Measures of location/spread. Standard. The histogram part is very easy but always causes problems.

EDIT

parts e) and f) are going to lead to an absolute bloodbath

part e) you had to calculate the prob using normal distribution (for 2 marks!)

part f) you had to say it seems reasonable since Prob from table is 0.40 but it isn't suitable since data is skewed

I think most candidates will get 1/4 at most.

Q6. DRV/Probability. Quite a confusing question, I think this will cause quite a few problems.

Q7. Venn. I thought this was pretty easy but I can see it causing a lot of problems.

Not really sure about the grade boundaries. It seemed pretty standard. Maybe 61 for an A.

Given the bloodbath that will happen I am inclined to reduce it down to 60/75 for an A

are you making a S2 mark scheme?

Reply 101

seana39223

I thought the paper was quite good, had a few challenging questions :smile:

Reply 102

Arsey

You will definitely get 2

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Reply 103

Arsey

Original post by amehta94

are you making a S2 mark scheme?

Nope Arsey don't do S2.

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Reply 104

Arsey

Original post by Humzah96

Arsey please respond

This was posted from The Student Room's iPhone/iPad App

Responded ...😉

To what, quote it.

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Reply 105

chignesh10

Original post by Arsey

Responded ...

To what, quote it.

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Arsey, for the avisha question...I answered it wrong and said whats the probability of winning with either die, so I got 1/3 for the blue die and 1/4 for the red die...
I didn't know that you had to find which combination of coin and dice is best...4 marks gone

Reply 106

Arsey

Original post by ljh950912

Any assumptions about 100 and 90 ums?

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Okay grade boundaries. This is a pure guess and I am not confident about them at all but what the hell...

75 = 100ums
68 = 90ums
61 = 80ums
53 = 70ums
45 = 60ums

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Reply 107

Part A

Original post by Arsey

Okay grade boundaries. This is a pure guess and I am not confident about them at all but what the hell...

75 = 100ums
68 = 90ums
61 = 80ums
53 = 70ums
45 = 60ums

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Sorry Arsey but think you're off on these, these are similar to June 12 grade boundaries and that was one of the easiest s1 papers there's ever been. This was much trickier and I think it will catch people out - I appreciate you're only having a guess though.

Reply 108

Arsey

Original post by Brutal_Pigeon

I think the paper felt OK overall, as people said there were some tough bits

Nasty kick in the teeth when I read Arsey's MS - the Normal Distribution question involving having to recharge the phone after 133 hours! I just said the probability of not having to charge at all until 133 hours, rather than the probability of not having to charge given that the phone did not require charging before then. Badly worded if you ask me!

Even so, not nearly as brain-addling as the second-last question. It seems the hardest bit of S1 is trying to work out the motive and rules of the increasingly arcane games people come up with!

Also, P([BnC]') has never come up before. I've never seen that notation, and neither had my teacher, at least in an S1 exam. Hopefully the markers will feel charitable.

I agree with part one, I think that will be more common than the correct answer. 2 marks.

Part 2. It was confusing but not that bad once you worked out what was going on.

Part 3. You should have come across not notation before, it was that hard to work out what it meant. There will be no charity.

1 mark for 0.44 one for method; either adding correct probs or just using venn (allowing ft)

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Reply 109

Arsey

Original post by Humzah96

This was posted from The Student Room's iPhone/iPad App

No marks for the first part.

I have no idea about the second part you need to be more specific.

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Reply 110

Arsey

Original post by Part A

I'm predicting 70-71 for 100 ums. I'm no expert but basing it against jan 12 grade boundaries. Be interesting to hear Arseys opinion on this..

This was posted from The Student Room's iPhone/iPad App

71 for 90ums would mean 67 for 80ums. I very much doubt they will be that high.

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Reply 111

MathMad

ahh no i put a as -90.7, because isn't it meant to be to 3sgf? will i not get a mark for it? and for 3c i got 5.92 seconds because thats 3sgf :/ will i get a mark for that? same with s.d i put 157 lol instead of 157.1. ???

Reply 112

Arsey

Original post by Part A

Being realistic, this was a much harder paper than Jan 12 (I did it a few hours before this exam).

I just looked at Arseys thread for S1 Jan 12 and he predicted it would be 75/75 for 100 ums and was a easy paper. Given that this was much harder, I would be inclined to say that 100 ums will be around 69-72.

P.S. for jan 12, it was only 72/75 for 100 ums so Arseys predictions aren't always correct. Props to him for uploading though, I'm just laying out the facts..

I have also said I can only guess at boundaries. I would rather not do it at all. All I can do is have a guess based on past papers and their boundaries. It is rare that I am more than 2ums for an A out. That said, some of the boundaries seem more extreme in recent sessions.

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Reply 113

lucien1995

Original post by Arsey

Okay grade boundaries. This is a pure guess and I am not confident about them at all but what the hell...

75 = 100ums
68 = 90ums
61 = 80ums
53 = 70ums
45 = 60ums

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For the first question I only put positive correation, more revision leads to better grades. Will I still get both marks? Please reply!

(edited 11 years ago)

Reply 114

Arsey

Original post by trentjoseph007

one of my friend did P(127<L<133) .. would he get any mark for it

Big fat zero

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Reply 115

Arsey

Original post by YathTheMagician

yes guys in q5e i got 0.4038 by doin 0.2981+0.2981=0.5962 then 1-0.5962=0.4038 but arsey show it is something els can someone help me out

I got 0.4038 too. That is correct.

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Reply 116

Arsey

Original post by chignesh10

and for f) i said her suggestion is invalid / wrong / unreliable as normal distritbution can only be used when there is symmetry about the mean, and as there is a very large positive skew, the normal distribution cannot be used. Is that right? and i said for a normal , mean = median but it isn't in this case

You will get 1 mark

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Reply 117

EL77

Original post by Arsey

0.75 isn't weak skew

for normal distribution to be suitable one criteria is that mean must be equal to the median (or very close to).

yes using 3(mean-median)/standard deviation, 0.75 is weak positive skew, because the closer the number to 0 the more symmetrical, so why couldnt you say mean = median roughly, due to roughly symmetrical data, supporting standard deviation?