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Content: Possible differences include: the subjects involved (Nationality? Age? Volunteers or paid subjects?) the time of day, the weather, the expectations of the experimenter (a powerful effect), and many other variables. Seemingly minor details could influence the outcome of an experiment. Replication failures may also expose what statisticians call a Type 1 error, a finding of statistical significance that is due to random error or luck of the draw. If an effect cannot be repeated reliably, scientists need to find out about it. That is why replications are performed. Until a phenomenon can be repro­duced reliably, even by researchers who are skeptical about it, one cannot be fully confident the finding will prove true in the long run.