What module to retake in maths

C1 and C2 if you can, but if you can only do 1, I'd suggest C2, because you got lower in that one.

But my S1 grade is the lowest as i have achieved an E. My C2 grade was a D.

But my S1 grade is the lowest as i have achieved an E. My C2 grade was a D.

Stats is way more work to resit because none of the content relates to A2- C1 and C2 are mostly stuff you do in more detail in C3 and C4 so your A2 lessons are kind of like revision. Also they look really easy when you've learnt the more advanced stuff. I suppose having stats at an E is going to pull your grade down, but the time saved not doing it could boost your A2 grades. Do you know what you're aiming for overall?

Trying to get a B as a minimum.

Trying to get a B as a minimum.

If you retake C1 and C2 after being taught the A2 content you should do well without a huge amount of revision. If you aim for a high A on both (so at least 85 UMS) then your AS total will be about 215 (I'm assuming you got a mid E on stats of 45 UMS). To get a B overall you need 420/600 UMS. This would mean you need 205 UMS overall in A2, so averaging 68.3 UMS on each A2 unit. That's only a high C on A2 which is very achievable if you're willing to work harder this year than last year.

To get an A overall with that same AS score of 215 you need 265 at A2 so an average 88.3 UMS which is a high A, which is more difficult. If you got 90 UMS on C1 and C2 instead of 85 the A2 average needed would drop to 85.

Overall, if you want a B then retake C1 and C2 to get at least 85 in each, and then you'll only need a high C at A2 to get a B overall- resitting stats isn't really necessary. If you would like an A then I think you should aim for 90 on C1 and C2 and get a mid to high A at A2. Resitting stats might be helpful in this circumstance because there'd be room to make more mistakes on C3 and C4- a low A or high B would still get you the A overall.