The nature of quasi-periodic pulsations in solar flares is poorly constrained , and critically the general prevalence of such signals in solar flares is unknown .
Therefore , we perform a large-scale search for evidence of signals consistent with quasi-periodic pulsations in solar flares , focusing on the 1 - 300s timescale .
We analyse 675 M- and X-class flares observed by GOES in 1-8Å soft X-rays between 2011 February 1 and 2015 December 31 .
Additionally , over the same era we analyse Fermi/GBM 15-25 keV X-ray data for each of these flares that was associated with a Fermi/GBM solar flare trigger , a total of 261 events .
Using a model comparison method , we determine whether there is evidence for a substantial enhancement in the Fourier power spectrum that may be consistent with a QPP signature , based on three tested models ; a power-law plus a constant , a broken power-law plus constant , and a power-law-plus-constant with an additional QPP signature component .
From this , we determine that \sim 30 % of GOES events and \sim 8 % of Fermi/GBM events show strong signatures consistent with classical interpretations of QPP .
For the remaining events either two or more tested models can not be strongly distinguished from each other , or the events are well-described by single power-law or broken power-law Fourier power spectra .
For both instruments , a preferred characteristic timescale of \sim 5-30 s was found in the QPP-like events , with no dependence on flare magnitude in either GOES or GBM data .
We also show that individual events in the sample show similar characteristic timescales in both GBM and GOES datasets .
We discuss the implications of these results for our understanding of solar flares and possible QPP mechanisms .