A confidence interval is calculated using the formula: Point estimate ± (Reliability factor × Standard error). The point estimate serves as the center of the interval, while the reliability factor determines the width based on the desired confidence level. The standard error reflects the variability of the sample statistic.

Sampling error, however, is not directly used in this calculation. It represents the discrepancy between the observed statistic and the true population parameter, which is why confidence intervals are employed to account for such variability. Thus, the correct answer is B.