RESEARCH · METHODS · EVIDENCE
Distributions and standard errors
Browse statistics lessons
- Statistics for research
- Center and spread
- Distributions and standard errors
- Statistical inference
- P-values and interpretation
- Critical values and test direction
- Compare means with t-tests
- Read t-test output
- Compare several means with ANOVA
- Read an ANOVA table
- Analyze categorical counts
- Read chi-square output
- Describe an association
- Read correlation results
- Interpret a regression model
- Choose a statistical method
- Statistics resources
A normal distribution is symmetric, with its mean and standard deviation determining location and spread. Not every dataset is normal. Examine plots and consider the model rather than assuming normality from a small sample.
Standard deviation describes observed spread. For independent observations, the standard error of a sample mean is estimated by s / √n. Correlated observations need an analysis that reflects that dependence. A larger sample does not repair biased sampling.
References: NIST statistical handbook