  This study shows that isoscaling, usually studied in nuclear reactions, is a
phenomenon common to all cases of fair sampling. Exact expressions for the
yield ratio $R_{21}$ and approximate expressions for the isoscaling parameters
$\alpha$ and $\beta$ are obtained and compared to experimental results. It is
concluded that nuclear isoscaling is bound to contain a component due to
sampling and, thus, a words of caution is issued to those interested in
extracting information about the nuclear equation of state from isoscaling.
