Sample vs population standard deviation
Use Sample when your numbers are a subset drawn from a larger population (most real-world data analysis). Use Population only when your data represents the entire group you care about, with nothing left out. Sample standard deviation divides by (n−1) instead of n, which corrects for the tendency of samples to underestimate true variability.
What standard deviation tells you
It measures how spread out your data is from the mean. A small standard deviation means values cluster tightly around the average; a large one means values are widely scattered. It's one of the most common ways to describe variability in statistics, quality control, and research.
Frequently asked questions
What's the difference between variance and standard deviation? Variance is the average squared deviation from the mean; standard deviation is simply the square root of variance, which brings it back to the same units as your original data.
Can I paste numbers from Excel? Yes — the field accepts numbers separated by commas, spaces, or line breaks.