I am analyzing some biochemistry kinetics data, and am trying to determine the confidence interval for a calculated parameter. I would be grateful for any help you could give, whether that is a quick answer or pointing me in the right direction or reference.

Basically, I have the following relationship,

z=f(x,y)=x/(1+c/y)

where c is a known constant. I have experimentally measured x and y, and have expected values and CI's for these variables based on number crunching by MATLAB. I can easily calculate the expected value of z, but do not know how to calculate the CI for z. I have tried to convert x and y into functions of common experimental measurements so that I can plug the whole equation into MATLAB for calculating CI's for z, but the nature of the two experiments used to determine x and y doesn't allow me to do this.

Is this an easy calculation, or a more involved one? The only statistics I have been exposed to is limited to the 1-2 weeks of bioengineering numerical methods course, so I'm not even sure what topic I should look up to find out how to analyze these data. If there is no quick answer, can you suggest a reference or topic I should further research?

Thank you for your help.