Explore statistics
Use the controls to see how changing the data or assumptions affects a calculation. Each applet explains the results beside its plots.
Three samples, three correlations
Start with data, means and uncertainty
A sample contains individual observations. Its mean estimates the population mean. Compare repeated samples to see how sample means vary, then use that variation to interpret intervals and tests.
- Sampling and standard error
- Confidence intervals
- A one-sample t test
- Statistical power and sample size
For relationships, begin with correlation, then explore regression. The z-test pages cover the special model where population SD is known.