OCR MATHS PURE + STATS A-LEVEL official thread

Yes! Just assumed my method was wrong

What you had to do it use 0.01 so then it was (1.03)^0.5 then it’s sqrt(103)/10 so just time the answer by 10. I started with 34 and realised it was wrong

I did proof by contradiction, assume that it was prime, then I said, let n=2k, where k greater than 2, then I put 2k into the equation 2^n - 1, which simplified to (2^k+1)(2^k-1), which was a product of 2 numbers, so not prime, so basically I said by contradiction, that her statement was correct

I think that's what I should've done, seems right enough, didn't realise at the moment :/

Did anyone get 5.20 for the volume?

The range value of K for the probability of young people vs old people in said something like 1/6 <= k <= 3
Not sure why again

And why would the data be useful for university students? (1)
And is it reliable? (2)

for the integral of u = sqrt(x)-1, did anyone get, 2(sqrt(x)-1) + 2ln(sqrt(x)-1) + c?

I think I got 4.5 for standard deviation of 62 - 72 with mean 67g question. Just realised this is wrong as i did p(X<62) = 0.125 rather than = 0.25 ( it was 25% either side not 12.5% - stupid mistake)
I got p = 0.068 for the prob mass < 530g question
Was r for the volume question 1.52? I forgot to sub back in to get Volume.
I got reject H0 for pollutant question as 0.04something... > 0.025
Proof if n is even, then 2^n - 1 is not prime. if even: n = 2k, so (2^2k) - 1: (2^k + 1)(2^k - 1), so as k> 1 then these are factors not equal to 1 or 2^2k -1, thus not prime.
Couldnt do the subsitution question... subbed through then tried using discriminant but still didnt end up with correct x values.
n = 1239 for last stats question
Integration of the polynomial P(x) denominator was 4ln(p(x)) + c

I got 1/4ln(p(x)) + c? I don't know whos wrong here

for the one where you had to use the substitution of u to find the polynomials, did anyone get x = 1/2 and x = -1/3? and reject the others because the discriminant was less that 0

Do you include 99 in the calculation for mean as it was an outlier

I did. But then my reason for median being better than men was because it reduces the risk of outliers skewing the results.

Does anyone know whether the grade boundaries are likely to be higher or lower than last years?

I think I got 4.5 for standard deviation of 62 - 72 with mean 67g question. Just realised this is wrong as i did p(X<62) = 0.125 rather than = 0.25 ( it was 25% either side not 12.5% - stupid mistake)
I got p = 0.068 for the prob mass < 530g question
Was r for the volume question 1.52? I forgot to sub back in to get Volume.
I got reject H0 for pollutant question as 0.04something... > 0.025
Proof if n is even, then 2^n - 1 is not prime. if even: n = 2k, so (2^2k) - 1: (2^k + 1)(2^k - 1), so as k> 1 then these are factors not equal to 1 or 2^2k -1, thus not prime.
Couldnt do the subsitution question... subbed through then tried using discriminant but still didnt end up with correct x values.
n = 1239 for last stats question
Integration of the polynomial P(x) denominator was 1/4ln(p(x)) + c

is it just me who got 1238 for the last one because when I subbed in 1239 back into the equation, the probability was slight greater than 0.025 when it said it had to be less than 0.025?