Statistics Calculators
6 calculatorsAnalyze data with calculators for probability, distributions, descriptive statistics, and statistical tests.
Frequently Asked Questions
- What is a normal distribution?
- A normal distribution (bell curve) is symmetric around the mean, where about 68% of values fall within one standard deviation, 95% within two, and 99.7% within three.
- What is the difference between population and sample standard deviation?
- Population standard deviation divides by N; sample standard deviation divides by N-1 to correct bias from estimating the mean. Use sample (s) when working with a subset of data.
- When do I use a z-score vs a t-score?
- Use a z-score when the population standard deviation is known or the sample is large (n ≥ 30). Use a t-score when the population SD is unknown and the sample is small.