AP Stats Unit 1

Variable

A characteristic or attribute that can assume different values

Categorical Variable

A variable that places individuals into one of several groups or categories

Quantitative Variable

A variable that takes numerical values for which arithmetic operations make sense

Distribution

Describes how the values of a variable are spread or distributed

Center

A measure that identifies the middle of a data set

commonly the mean or median

Spread

A measure of how much the data values vary

includes range, interquartile range (IQR), and standard deviation

Outlier

An observation that lies outside the overall pattern of the data

Skewness

Describes the asymmetry of a distribution

can be left-skewed (negative) or right-skewed (positive)

Symmetry

A distribution is symmetric if the left and right sides are approximately mirror images

Percentile

The value below which a given percentage of observations fall

Z-score

The number of standard deviations a data point is from the mean

Boxplot

A graphical representation of the five-number summary: minimum, Q1, median, Q3, and maximum

Histogram

A bar graph that displays the frequency of data within equal intervals

Stem-and-Leaf Plot

A method of displaying quantitative data that retains the original data values

Dotplot

A simple display where each data value is shown as a dot above its location on a number line

Mean

The arithmetic average of a set of values

Median

The middle value when data are ordered from least to greatest

Mode

The value(s) that occur most frequently in a data set

Range

The difference between the maximum and minimum values

Interquartile Range (IQR)

The difference between the third quartile (Q3) and the first quartile (Q1)

Standard Deviation

A measure of the average distance of data points from the mean

Variance

The square of the standard deviation

measures the spread of data points

Five-Number Summary

Consists of the minimum, Q1, median, Q3, and maximum