non-parametric data for reference ranges


I am very new to statistical analysis, but am very excited to to be learning it. I am working on finding reference ranges for some mammalian blood work. I hope this is the appropriate place to post my query, otherwise, my apologies.

I have successfully found my reference ranges for all my normally distributed material. Now I am working on my non-parametric categories. I am under the impression that I will find the reference ranges by arranging my data points in order and demarcating the 2.5 and 97.5 percentiles, followed by finding IC95% for each of those values (I may have misinterpreted this). Then using the upper value of the IC95% from the 2.5 percentile and the lower value from the 97.5, I have a developed a presumed reference range. I would be grateful for any guidance on the appropriate way to calculate these values.

Additionally, everywhere I look to find a calculation for IC95% I get a slightly different equation. Could someone offer an accurate formula?

I have also been led to believe that this may be an appropriate time to use bootstrapping for my non-parametric data. Unfortunately, I am struggling to understand how this would help or how this works.

Thank you for all your help and time!