In High Throughput Screening, the experimenter designs the system to provide tools to measure the samples prepared against his chosen criteria. Those that match or exceed his criteria are 'passes' or hits, those that don't measure up are failures.
However, in another mode, High Throughput systems can be set up to 'Characterise' which is more common nowadays: detailed measurements are made on all samples and no criteria are set up to screen out samples. This is usually done to develop an understanding of the underlying processes or to build models that relate measurements against desirable properties.
Stephen Bysouth www.automaxionltd.com