Why run in duplicate?
In general, authors of scientific reports must state the number of replicate experiments and replicate samples. Samples are run in replicates to measure variation in an experiment. This also allows statistical tests to be performed on the data evaluate differences.
Replicate samples from identical experimental conditions can be thought of in terms of samples from different individuals or independent samples (biological replicates). They can also be thought of in terms of repeated measurements of the same sample (technical replicates) that support measurement of variation within the protocol, user, or equipment.
Study designers thinking about running ELISAs should consider both biological as well as technical replicates. Whereas biological replicates will show variation within a population, technical replicates demonstrate variability within the protocol. This variation within a single plate or assay can be studied and reported as intra-assay variation.