CCEA S1 13 June

My answers

1 (i) 0.7514474781
(ii) 0.2191721811
(iii) Not all seasons will have as much a chance of cross winds than in winter

2 (i) 59.91809919
(ii) Median = 65 (I didnt know whether to do 6 divided by 36 and add it onto 60 to get the median so i didnt, you proabbly had do if its 4 marks)

3 (i) 0.220418077
(II) 0.357768112
(iii) 0.06124145229

4 (ii) E(x) = 4 Var(x) = 0.8
(iii) E(y) = 16 Var(y) = 0.8

5 (ii) 32 over 15
(iii) 49 over 256

6(i) 0.1151
(ii) -0.524
(iii) 58.49%

7(i) 9 over 25
(ii) 0.09
(iii) 0.874
(iv) 0.25
(v) 1 - P(A) - P(C) (Didnt know how to include B)
(vi) 0.3
(vii) 0.4

1(ii) = 1 - (PX=1) - (PX=2) yeah?

for 6(ii) i wasnt overly sure how to do it. what i did was put Z(2) = -Z i.e Z(2) now on the positive x axis, found (z<Z(2)) gives u 0.7 (If Z(2) = -Z, the area to the right of Z(2) will equal 0.3) and the closest figure i got was 0.524, which actually gave me a probability of 0.699 but i just took whatever figure in the table closest to 0.7. So P(z<0.524) =0.699(Rounded to 0.7). Because Z(2) is 0.524, Z - 0.254. Ive a feeling a i have done something wrong because i could get no figure givin a probablility of 0.7, plus I think a question wouldnt be as complicated as I made it out to be

1(ii) = 1 - P(x=0) - P(x=1)

You might have got the right z values but the answer had to be an upper weight limit i.e the value of x. I got 59.6 grams.

And I wrote for 6iii was impossible?

I think i mighta done 1 - P(x=0) - P(x=1) and I completey forgot to take it back to X lmao, for the percentage I did 1-0.3(eggs in small range)-0.1151(eggs in big range) = 0.5849 times by 100 to get % = 58.49%

for 5(iii) X is the distance more than 3m he jumped i.e if x can be any value from 0 to 4 inclusive, he can jump from 3m to 7m, the upper limit was supposed to be 4, lower limit 3, as when x is 3 he is jumping 6m and when 4 he is jumping 7m

What did you write for the median? I dont know if 65 is correct or not as the median value was the 6th value out of 36 for 60<W<70. I didnt know whether to do 6/36 and add it on to 60 or just take the midpoint, it seems more realistic to do the 6/36 and add it on but sure... what probability q's did u mess up?

I forgot how to do probability of A and B, i assumed u multiplied them but the formula booklet said u had the multiply like A by B given A r sumtin. I thought it was handy cus u could just check in the table if your right, 18/200 got a sphere 220 on 18 month contract, so 0.09 is correct, i would have messed up that whole 1 if we werent given all that information

What did you write for the median? I dont know if 65 is correct or not as the median value was the 6th value out of 36 for 60<W<70. I didnt know whether to do 6/36 and add it on to 60 or just take the midpoint, it seems more realistic to do the 6/36 and add it on but sure... what probability q's did u mess up?

Yeah I think everyone hates them probability questions! The info definitely helped a lot! Pretty confident I've got over 70% at least.

I used the formula for median from a table, which is
L1 +(c(n+1/2 -sum of freq up to but not including median class) with that bracket divided by the frequency of median class.

final answer came out as 61.6666 mm, rounded to 61.7mm.
my answer for 1ii) was 0.0294, anyone else get the same? Didn't read the question properly at 6iii, put it as 0.585, should get one of the two marks. Three of my q7 answers seem to be off (totaling 8 marks), but hopefully ill get some working marks.
All in all a much better paper than January, think I'll have got my A this time around.

I ballsd up my C2 so i need in and around full marks. Raging i didnt repeat C2 in january cus it was easy and I know id have my A for definite. I hope i got the median right and the right answer written for 1(ii) or else ill have no A

Got 98 in jan C2

Got 98 in jan C2