chapter 2

histogram

A graphical depiction of a frequency or a relative frequency distribution for a numerical variable; series of rectangles where the width and height of each rectangle represent the interval width and frequency (or relative frequency) of the respective interval.

polygon

For a numerical variable, a graph of a frequency or relative frequency distribution in which lines connect a series of neighboring points, where each point represents the midpoint of a particular interval and its associated frequency or relative frequency.

a bar chart and a pie chart are two widely used graphical representations for

a categorical variable

pie chart

a circle that is cut into slices, or sectors, such that each sector is proportional to the size of the category we wish to display

two common tabular and graphical methods that help us summarize the relationship between two categorical variables

a contingency table and a stacked column chart

bar chart (column chart)

a graph that depicts the frequency or relative frequency of each category of a categorical variable as a series of horizontal or vertical bars, the lengths of which are proportional to the values that are to be depicted

frequency distribution

a table that groups the observations of a variable into categories or intervals and records the number of observations that fall into each category or interval

ogive

connects a series of neighboring points where each point represents the upper limit of a particular interval and its associated cumulative frequency or cumulative relative frequency

line chart

displays a numerical variable as a series of consecutive observations connected by a line

when presented with a categorical variable, it is often useful to summarize the data with a

frequency distribution

stacked column chart

graph of a contingency table; depicts more than one categorical variable and allows for the comparison of composition within each category

scatterplot

graphical tool that helps in determining whether or not two numerical variables are related in some systemic way. each point in the diagram represents a pair of observations of two variables

scatterplot with a categorical variable

modifies a basic scatterplot by incorporating a categorical variable

contingency table

shows the frequencies for two categorical variables, x and y, where each cell represents a mutually exclusive combination of the pair of x and y observations