  Stochasticity of bright stars introduces uncertainty and bias into derived
structural parameters of star clusters. We have simulated a grid of cluster
$V$-band images, observed with Subaru Suprime-Cam with age, mass, and size
representing a cluster population in the M31 galaxy and derived their
structural parameters by fitting King model to the surface brightness
distribution. We have found that clusters less massive than $10^4 M_\odot$ show
significant uncertainty in their core and tidal radii for all ages, while
clusters younger than 10 Myr have their sizes systematically underestimated for
all masses. This emphasizes the importance of stochastic simulations to asses
the true uncertainty of structural parameters in studies of semi-resolved and
unresolved clusters.
