What term denotes the likelihood of conclusively demonstrating an effect if one exists?

• A. Validity
• B. Statistical power
• C. Reliability
• D. Effect size

Answer: (B)

Statistical power is the likelihood that a study will detect an effect if one truly exists. It answers the question of how sensitive a test is to finding real effects, given factors like the true effect size, sample size, and the chosen significance threshold. Larger true effects, bigger samples, and less noise raise power, while a stricter alpha level lowers it. A common target is about 80% power, which means there’s an 80% chance of detecting the effect if it’s there, reducing the risk of a Type II error (failing to observe a real effect). Validity concerns whether the test measures what it’s supposed to measure; reliability concerns consistency of measurements; and effect size is the magnitude of the effect itself. These concepts relate to measurement quality or magnitude, not directly to the probability of detecting the effect, which is what power captures.