Final answer:
An experimental result is considered statistically significant when it is unlikely to occur by chance, with a conventional threshold of less than five percent probability.
Step-by-step explanation:
An experimental result is called statistically significant when the result is unlikely to be due to chance alone. To determine this, a statistical analysis is conducted after an experiment to assess the differences between the experimental and control groups. If the likelihood that these differences occurred by chance is less than five percent, researchers generally consider the result as statistically significant. This threshold helps limit the occurrence of making a "false positive" claim to less than five percent.
Statistical significance is crucial in experiments, including those in fields like medicine, where the efficacy of a drug is tested by comparing outcomes between experimental and control groups. A double-blind experiment, where neither participants nor researchers know who received which treatment, is considered the gold standard in such trials to prevent biases from influencing the results.