Which concept describes the probability that the true effect lies within the calculated interval?

• A. Statistical significance
• B. Confidence level
• C. Confidence interval
• D. Margin of error

Answer: (B)

The concept being tested is how we interpret a confidence interval and its level of certainty. The probability that the true effect lies within the calculated interval is described by the confidence level. For example, a 95% confidence level means that if you repeated the study many times and built a new interval each time, about 95% of those intervals would capture the true population effect. The interval itself is the range we compute, while the confidence level describes how often such intervals would contain the true value in the long run.

The other terms don’t fit this exact interpretation: statistical significance concerns whether an observed effect is unlikely under the null hypothesis; a confidence interval is the actual range computed; the margin of error is half the width of the interval, reflecting precision.