CA May 2015 Paper 1

[Darragh Kelly]

Hi

Regarding the reasonableness checks at the end of the paper regarding the % change in swim times and % change in lambda,swim. I'm just struggling to get my head around why the % change in lambda, and each swim time are the same? If they were related by a simple linear relationship I would agree but the formula for calculating the adjustment parameter for swim is: (1/(1+2*EXP(lambda*d))+2/3). So its see/stand over the fact if lambda decreased by 50%, swim time should also decrease by 50%?

Thanks,

Darragh

 

[Sarah Byrne]

Hi Darragh

I think you're referring to a check in the spreadsheet here comparing the ratio of the swim lambda and the change in the swim times. Given they are both changing by the same factor it's reasonable that the adjustments are the same. The revised lambda is used to calculate a new swim time just by multiplying by the updated adjustment parameter. The check is that the adjustment parameter has the same impact on swim times and lambda which passes.

As ever, the bigger picture is that you don't need all comments/checks for full marks. This is now quite an old style paper and I'd encourage you to focus on more recent papers where you have the mark scheme. I'd also expect a new paper to explain why these are reasonable results rather than just stating these as reasonable without further comment.

Sarah