Using under-sampled data, what determinations can be made about the Nyquist rate (correct sampling rate)?
This may be a trivial answer, but you can of course use the aliasing information to determine the correct sampling rate, given that you know that the signal is undersampled. In the simplest case, given that the signal appears to be at $k f_s,\ k &lt; 0.5$ one can devise that the frequency of the signal is $(1-k)f_s$. In general it may be at $(N \pm k)f_s$ for some integer $N$.