## R

### r

The symbol given to the pearson correlation coefficient.

### r^{2}

The symbol given to the coefficient of determination, the proportion of variability accounted for by a correlation and the square of the pearson correlation coefficient.

### Random sampling

The act of selecting individuals from a population without bias.

### Range

The difference between the highest and lowest value (a measure of variability and an example of a descriptive statistics).

### Related data

If data are related, an observation of one variable can be linked to a corresponding observation of a second variable. Obviously, this means that there must be the same number of observations in each set of data (see also unrelated data).

### Research hypothesis

An educated guess to a research question.