
Diagram:
Normal distribution with standard deviations.

Diagram:
Type I error. The means of sets of sample data from a population are normally distributed. If the mean of an experimental data set falls outside a certain preset point (usually 0.05), we decide that it is not likely to be within a normal variation of sample means. We reject the null hypothesis.

Diagram:
Alpha and beta error. Alpha error is the area in the tail of the sample mean distributions, bounded by the critical value. Beta error is in the tail of the experimental data set means, bounded by the critical value. This is the likelihood that we would accidentally say there was no difference between the two populations when there actually was.

Diagram:
Creating a confidence interval, part 1: establishing the lower bound.

Diagram:
Creating a confidence interval, part 2: adding the upper bound.

Diagram:
The chisquared test, used to test association between categorical variables.

Diagram:
Kappa: a nonparametric test for assessing interobserver variability.