Mr K's OCR (not OCR MEI) S1 answers May 2012

Mr K's OCR (not OCR MEI) S1 answers May 2012


1. (i) r = -0.709 (4 marks)

(ii) y = -0.0185x + 8.5742

Estimate £3394 (4 marks)

(iii) Correlation does not imply causation (1 mark)


2. Mean = 1.53 kg

Standard deviation = 14.7 g (6 marks)


3. (i) 22.5 (1 mark)

(ii) w = 0 and x = 0 (2 marks)

(iii) 40 or 40.75 (2 marks)

(iv) Gives a visual display of distribution OR original data preserved (1 mark)

(v) Shows spread/IQR/median more clearly (1 mark)


4. (i) Top pair of branches Red 4/5 and Black 1/5

Bottom pair of branches Red 1 and Black 0 (2 marks)

(ii) 1/3 (3 marks)

(iii) 4/5 (2 marks)


5. (i) (a) 1 (1 mark)

(b) -1 (1 mark)

(ii) 0 (3 marks)

(iii) Completely agreed, Completely disagreed, No agreement (3 marks)


6. Profit = £110 (5 marks)


7. (i) (a) 2520 (2 marks)

(b) 720 (3 marks)

(ii) (a) 21 (1 mark)

(b) 10/11 (3 marks)


8. (i) 0.825 (2 marks)

(ii) (a) 0.265 (2 marks)

(b) 0.168 (6 marks)


9. (i) (a) 0.0590 (3 marks)

(b) 0.410 (3 marks)

(ii) (a) 0.0951 (2 marks)

(b) 0.513 (3 marks)


These answers were produced by my colleague Mr K and not by me so there is probably little point asking me about them. Hope you find them useful though!

for question 4i i wrote 5/5 and 0/0 on the branches will the mark still be awarded?

For Q7i)b) I was told that the answer is 2 * 9P4 = 720

But I wrote... 4! + 4!*2 = 72. I drew out spaces, and realised that if there was 1 vowel, then 1 can fit at the end, then the rest in 4*3*2*1, and if there were 2 vowels, it would be either of the 2 vowels fit at the end, with 4*3*2*1 in the other 4 spaces. What did I do wrong and would I get any marks for it?

hey Mr M, i forgot to use the regressing equation to get the estimate, and i worked out question 9 given that the clock was turned 5 minures BEFORE midnight. but i did the right method, so how many marks do you think i dropped? i also did a weird method for part 8b and i think i may get a couple marks there. all in all i think i dropped about 25 marks in total, what grade is that? usually?

I didn't produce these answers so I'm not sure. I can't guess grade boundaries but the suggestion is this paper was harder than usual so the boundaries should be generous.

I didn't produce these answers so I'm not sure. I can't guess grade boundaries but the suggestion is this paper was harder than usual so the boundaries should be generous.

Made my....LIFE My university place counts on S1

Already asked, but can anyone tell me why 4iii is 4/5? my working gets me 2/3:

Red, Red, Red which is (5/6 x 4/5 x 3/4)

+

Red, Black, Red which is (5/6 x 1/5 x 1)

That makes 1/2 + 1/6 = 2/3

I must be doing something stupid, but I can't see what it is.

Already asked, but can anyone tell me why 4iii is 4/5? my working gets me 2/3:

Red, Red, Red which is (5/6 x 4/5 x 3/4)

+

Red, Black, Red which is (5/6 x 1/5 x 1)

That makes 1/2 + 1/6 = 2/3

I must be doing something stupid, but I can't see what it is.

I made this mistake at first as well but you don't take into account the 5/6 because it's already a given probability, i.e '...given that the first counter is red.'

Calculating just (4/5 x 3/4) + (1/5 x 1) gives 4/5

That's not a very good explanation though haha, can anybody elaborate for me?

I just checked it myself.

The possible values of z were (3)8 or (3)9 but there is a big gap to the next number 46. This puts the upper quartile into the 40s.

I taught this module, and did this paper myself today. I haven't got my answers with me, but they look correct with the exception of this one (q3) - I think the students querying this are correct. For a list of 14 numbers the median is the mean of the 7th and 8th, the LQ is the 4th (so 23 is the correct answer for (i) ) and the UQ is the 11th number. (The 'median' of the 7 above the median). That is the number marked as 3|z which can only represent 38 or 39. The gap to 46 is irrelevant.

By the way, thanks for your efforts Mr M, I know many of my students appreciate it.

I taught this module, and did this paper myself today. I haven't got my answers with me, but they look correct with the exception of this one (q3) - I think the students querying this are correct. For a list of 14 numbers the median is the mean of the 7th and 8th, the LQ is the 4th (so 23 is the correct answer for (i) ) and the UQ is the 11th number. (The 'median' of the 7 above the median). That is the number marked as 3|z which can only represent 38 or 39. The gap to 46 is irrelevant.

By the way, thanks for your efforts Mr M, I know many of my students appreciate it.