Ap Stats-Vocab List 1 (Group 7)

Time Plot

A graph that plots each observation against time. Time is always on the x-axis and the other variable is always on the y-axis.

Variability

A measure of the spread of a data set. A larger set of data gives a smaller spread. As long as the population is much larger than the sample, the spread of the distribution is almost the same for any population size.

Unimodal

Describes a distribution with one peak or hump. A uniform distribution cannot be classified as unimodal, but rather a distribution with no mode.

Bimodal

Describes a distribution with two peaks or humps. Does not necessarily have to be two modes, but rather two clusters or humps.

Spread

Describes the variability of the data in a distribution. IQR, range, standard deviation, and variance are common measures of spread. For skewed distributions, it is better to use IQR and the median to describe the spread rather than the mean and standard deviation.

Modes

The major peaks or relative extrema of a distribution. This helps describe the shape of a function. A distribution can be classified as either unimodal, bimodal, trimodal, or uniform depending on the number of peaks.

Center

The value that divides the distribution in half with one half including larger values and the other half including smaller values. Two common measures of center include mean and median. Mean is resistant meaning that it does not respond strongly to to changes. The median is not resistant.