  The statistical examination of solar flares is crucial to revealing their
global characteristics and behaviour. Such examinations can tackle large-scale
science questions or give context to detailed single-event studies. However,
they are often performed using standard but basic flare detection algorithms
relying on arbitrary thresholds. This arbitrariness may lead to important
scientific conclusions being drawn from results caused by subjective choices in
algorithms rather than the true nature of the Sun. In this paper, we explore
the effect of the arbitrary thresholds used in the GOES (Geostationary
Operational Environmental Satellite) event list and LYRA (Large Yield
RAdiometer) Flare Finder algorithms. We find that there is a small but
significant relationship between the power law exponent of the GOES flare peak
flux frequency distribution and the flare start thresholds of the algorithms.
We also find that the power law exponents of these distributions are not
stable, but appear to steepen with increasing peak flux. This implies that the
observed flare size distribution may not be a power law at all. We show that
depending on the true value of the exponent of the flare size distribution,
this deviation from a power law may be due to flares missed by the flare
detection algorithms. However, it is not possible determine the true exponent
from GOES/XRS observations. Additionally we find that the PROBA2/LYRA flare
size distributions are artificially steep and clearly non-power law. We show
that this is consistent with an insufficient degradation correction. This means
that PROBA2/LYRA should not be used for flare statistics or energetics unless
degradation is adequately accounted for. However, it can be used to study
variations over shorter timescales and for space weather monitoring.

Solar and Stellar Astrophysics