How to use: Calculate confidence interval range around a sample mean. Enter Value (sample mean/average), Sample Size (number of observations), and Standard Deviation (measure of spread). Calculator uses 95% confidence level (1.96 z-score). Results show: Lower Bound and Upper Bound defining the interval. Formula: Mean ± 1.96 × (Std Dev / √Sample Size). Interpretation: 95% confident true population mean lies within this range. Example: Mean=100, n=50, std dev=15 → interval ≈ 95.8 to 104.2. Larger samples = narrower intervals (more precise). Applications: political polling (candidate support range), clinical trials (treatment effect range), quality control, market research. Essential for statistical inference and uncertainty quantification.