Sharpe ratio in Quant ?

Hi everyone, I noticed that in Quant, Sharpe, SFR and other ratios are introduced but with the standard deviation of a portofolio… Well my question is simple : is it possible to use Sharpe or SFR in Quant using the standard deviation of a population OR standard error of the sample (∂^2/n) ? Thanks

The Sharpe ratio involves the risk-free rate, which doesn’t make much sense unless you’re talking about security (or portfolio) returns.

He probably means something to measure the variablitity of a mean.

Something along the lines of SNR or CV.