# Student Resources

## Glossary

**Asymptote:** A line that a graph approaches, but does not reach, as *x*- or *y*-values increase in a positive or negative direction.

**Density Curve: **A mathematical model of a distribution. The total area under the curve, by definition, is equal to 1, or 100%. The area under the curve for a range of values is the proportion of all observations for that range.

**Distribution:** The way in which the data is spread.

**Empirical Rule:** The empirical rule, also known as the 68-95-99.7 rule, describes the spread of data in a normal distribution given the mean and standard deviation. 68% of the data will fall within one standard deviation of the mean, 95% of the data will fall within two standard deviations of the mean, almost all (99.7%) of the data will fall within three standard deviations of the mean.

**Frequency:** How often a data point appears in the data set.

**Mean: **A measure of central tendency for a one-variable data set. It is found by dividing the sum of all values by the number of values.

- (x-bar) represents the mean of a
.__sample__ - μ (Pronounced "mu" ) represents the mean of a
__population.__

**Mean Absolute Deviation:** A measure of spread for a one-variable data set that uses absolute value to eliminate the effect of the different signs of the individual deviations.

**Normal Curve:** The graph of a normal distribution.

**Normal Distribution:** A symmetric bell-shaped distribution.

**Percentile:** The percentage of values in a data set that are below a given value.

**Population:** The whole group from which a sample is taken.

**Sample:** A selection taken from a larger group, or population, to examine in order to find out characteristics about the population.

**Skewed Data:** Data that are spread out more on one side of the center than on the other side.

**Standard Deviation:** A measure of spread for a one-variable data set that uses squaring to eliminate the effect of the different signs of the individual deviations.

- "S" represents the standard deviation of a
.__sample__ - "σ" (lower case Greek letter "sigma") represents the standard deviation of a
.__population__

**Symmetric Data:** Data that are balanced about the center.