Edexcel S2 - 27th June 2016 AM

Oh dear rookie error... thank you!


Posted from TSR Mobile

Is this the last A level exam in general? From the people I know S2 is last. 27th June is damn late... Can't believe how quick college flew by. Seems like yesterday I was going to open days.

I don't have the answers I'm afriad they may well not be fractions, it's the method that's most important anyway I'll have a look at the answers in a bit and quote you again.

Just in case there's 3 functions.. in general, as you'd expect, there's only 1 x value, or one of the functions, such that F(X) = 0.75, so equating to any one of them won't work - you first have to work out which one it actually is, usually by trial and error (and testing the ranges of each function, to use C3 lingo).

Is this the last A level exam in general? From the people I know S2 is last. 27th June is damn late... Can't believe how quick college flew by. Seems like yesterday I was going to open days.

A distribution X is used to model the length, in mm, of the first tear of a uPhone charger, and the PDF is specified below. However, Wapple have been careless and have lost some key details of the PDF.

$kx(1-x)$ if $0 \leq x < 0.5$

$\frac{23}{40} - \frac{3x}{20}$ if $0.5 \leq x \leq b$

0 otherwise.

a) Given that b is the minimum value greater than 0 such that f(b) = 0, find the value of b.

b) Hence find the value of k.

c) Find the expected length of the tear and the standard deviation.

d) Find the interquartile range of the length of tears.

e) Wapple send out an inspector to 5 random people who had asked for refunds. If the tear is longer than 1mm for at least 3 customers, all five will be refunded (ignoring systematic/human error). Find the probability, to 2 s.f, of Wapple giving a refund to a random group of 5 customers who have complained.

Oh alright I see, But also; I just looked at the mark scheme for the question I asked you about and it said this:
M1: putting their line 2 or their line 3= 0.75

.... Would you get the same answer then? I'm a bit confused now . My apologies

Thank you!

a) b=23/6
b)k=2
c)1.39 and 0.867
d)1.73
e)0.686

correct?

You'd get a method mark for 'having the right idea'. (I haven't looked at the question properly so it could be that students either put the correct function on line 2 or line 3?

I saw another question about finding the mean and equating F(m) = .5 and this is what the mark scheme says:



So doesn't that suggest either equation would get the same answer?

Up to you whether you want to attempt the rest of the questions - the rest of the numbers don't come out so nicely but I'm getting some answers for it now.



S2 is pretty late, I think D2 and FP3 may be around the same time or later. (FP3 might clash with this, funnily enough).

a. b = 23/6

b. k = 2

c E(X) = 1.39. E(X^2) = 2.70. Var(X) = 0.77. Deviation = 0.88 (answers within that range, depending on rounding etc)

d. IQR question removed - takes too much time.

e. 0.69.






Well done the last bit should be 2 s.f but doesn't matter really. Just something to be wary of in the exam if they specify how many s.f you need.

k=2 I got