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Edexcel S2 - June 22nd, 2015 [Exam discusison thread]

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Jan 2014 INTL is horrid. 12 mark question at the end (one question, it's not split up at all) and a tricky one about hypothesis tests (a bit backwards).
Original post by Sapphire109
Lol thanks, but the thing I don't understand is that why is a=0?
Also for the past paper june 2007 question 1d, why is the answer 0 (is it because we are dealing with continuous random variable?)
Thanks again


for june 2007 yeah you are right it is because we are dealing with continuous random variable
Jan 15 ial, question 7, i did it and got it right after subbing values but when i did i used inequalities, I did
(29.5-0.2n)/(0.4rootn) >=2 now this gives n>=106.265... when it should be the other way around, can someone elxplain to me why the inequaliy sign should be switched? for
P(Z>(29.5-0.2n)/(0.4rootn) <= 0.0228 shouldn't the z-value be greater than 2?

also what are the grade boundaries??
(edited 8 years ago)
does anyone have link for jan 2015 IAL paper ?
I would consider the critical region to be the range of values of the test statistic for which we would reject H0. However, the mark scheme is quite weird on this one:
The critical region is the range of values or a test statistic or region wherethe test is significant
that would lead to the rejection of H0.

To me the bold underlining here implies that what I have stated would not be accepted; rather they would prefer just the "range of values". But surely that isn't specifying..values of what? And yet it implies the acceptability of "a test statistic that would lead to the rejection of H0" which clearly isn't referring to a region. The book definition is basically identical to mine, but then again in the book they do not define a statistic in the manner that is required to get marks either.
Someone help me with 5e

https://57a324a1a586c5508d2813730734691051ac35fd.googledrive.com/host/0B1ZiqBksUHNYZ3M4QzJ0N19IeHc/June%202013%20%28R%29%20QP%20-%20S2%20Edexcel.pdf
Original post by Maham88
does anyone have link for jan 2015 IAL paper ?


https://drive.google.com/folderview?id=0B23NLD5L6099fnpGb0N0M19EM0dOY3Z6cnRfc1NjRzEzeEVJb0RlN2JJbTUwNDltci1qTDQ&usp=sharing&tid=0B23NLD5L6099flZuR3hLRUdnNXJfbDBPTjJ2SWR4VlJuMzA4WS1wN3NSU1JXU3hkV0kteTA

https://drive.google.com/folderview?id=0B23NLD5L6099fmlSR1pkQ3BPSWN4bGFRVzVZd0hHb0FQQjl0WjBrNWFOV3VPbjVCQmRUaTg&usp=sharing&tid=0B23NLD5L6099fjFxaWtjaXpKd2VlTUdkZGp4QzA2RTdyQ3VMQkMxck1FZW1NMDJ4OHo0QjQ
Original post by TheGreyPhysicist

thanks
Original post by nayilgervinho


You just need to multiply two probabilities together. The probability of no customers joining the queue in a 4 minute interval (you will need to calculate the mean for this adapted Poisson distribution using the fact that 3 customers join every 10 minutes) and the probability that Bethan takes less than 4 minutes.
Can someone please explain question 7 to me of the JAN 15 IAL paper? I understand to change it into normal distribution but I don't understand how to solve the equation with the square of n?
IMG_20150620_151844.jpgcould someone explain how to do the last part of this question?
Hey guys has anyone done June 2014 that could explain question 3.d. to me? I really dont understand why the fact that the observed value is not within the critical region supports the companies claim? i always thought it was the other way round ahhhh
How fussy are they on what letter you use to define/state a distribution. Markscheme doesn't say anything about explicitly not accepting other letters. I'm asking as I just did a question in three parts where they went from X -> Y -> T and I used X -> X -> Y but got all of the same numbers and inequalities.
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MATTTT
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Parts C and D. anyone got any tips on how to draw that graph? And how did they work out mode is 2?? I know it's the highest point but how did they get the value, because you can't tell by looking at the graph as it could be 2.1, or 2.5 or 2.8 ??

Ok figured it out, you differentiaite and make gradient =0. BUT HOW DO I DRAW THAT GRAPH IN THE EXAM?
(edited 8 years ago)
1f3aeda63c2367c1fa5cee0c9d9bc580.png78.9KB
Jan 2015 IAL was so hard... For me anyway
Original post by Maham88
thanks


no probs :smile:
think there's more definitions to learn than there is actual content such BS it's supposed to be maths not english and i'm sat here with almost 3 pages of definitions to learn
can someone explain part c please
battery.PNG143.4KB
Original post by letsplayray
If the probability is less that or equal to you add .5, if it is greater than or equal to you minus 0.5 - you have to get the probability into the form of equal to greater/less than


Ok thanks, however in the book page 86 example 5 it says P(X>30) = P (Y>30.5)
but I was thinking wouldn't P(X>30)=P(X>/29)=P(Y>/28.5)
Original post by 1 8 13 20 42
I would consider the critical region to be the range of values of the test statistic for which we would reject H0. However, the mark scheme is quite weird on this one:
The critical region is the range of values or a test statistic or region wherethe test is significant
that would lead to the rejection of H0.

To me the bold underlining here implies that what I have stated would not be accepted; rather they would prefer just the "range of values". But surely that isn't specifying..values of what? And yet it implies the acceptability of "a test statistic that would lead to the rejection of H0" which clearly isn't referring to a region. The book definition is basically identical to mine, but then again in the book they do not define a statistic in the manner that is required to get marks either.


i think you would get the marks, but here the range of values of a test statistic is the z values, so "a test statistic..." makes sense because if you get a z value of like 3 lets say, and CR is X<=4 then your statistic has lead to the rejection of H0. so just keep it to range of values i guess, will save you 0.003 seconds from writing "of the test statistic :tongue:

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