Formulas & Definitions are in alphabetical order

When the bulk of the data clusters around the mean in a normal distribution (or bell-shaped curve), the standard deviation can be used to approximate how much of the data will cluster around the mean.

1. -65% of the data values will fall within 1 standard deviation from the mean

2. -95% of the data values will fall within 2 standard deviations from the mean

3. -99.7% of the data values will fall within 3 standard deviations from the mean

The result of multiplying a series of descending natural numbers; useful in computing the number of combinations or permutations between

The average of a sample

The midpoint of a ranked dataset

The midpoint is the midrange between the highest and lowest data points.

Most frequently occurring value of x

The mean of the squared deviations (using the degrees of freedom as the denominator) in a sample

Standardized measurement of dispersion or variation around the mean

The positive square root of the variance in a sample