Key Concepts

• Histograms are a graphical way to display a data set that has been organized in a frequency table.
• Frequency polygons can be used to show changes in frequencies for quantitative data for continuous data sets.
• Time series graphs are a plot of paired data (time and value) and can be used to show trends over time.

Glossary

frequency: the number of times a value of the data occurs

frequency polygon: looks like a line graph but uses intervals to display ranges of large amounts of data

frequency table: a data representation in which grouped data is displayed along with the corresponding frequencies

histogram: a graphical representation in x-y form of the distribution of data in a data set; x represents the data and y represents the frequency, or relative frequency. The graph consists of contiguous rectangles.

interval: also called a class interval; an interval represents a range of data and is used when displaying large data sets

midpoint: the mean of an interval in a frequency table

paired data set: two data sets that have a one to one relationship so that both data sets are the same size, and each data point in one data set is matched with exactly one point from the other set

relative frequency: the ratio of the number of times a value of the data occurs in the set of all outcomes to the number of all outcomes

time series graph: a graph for a paired data set where the x-axis represents time and y-axis is the value of the variable. Time series graphs help to show trends.