Section 2.3 Summary

1. A cumulative frequency distribution shows the total number of observations less than or equal to the category value (for a discrete variable) or the upper class limit (for a continuous variable). A cumulative relative frequency distribution shows the proportion of observations less than or equal to the category value (for a discrete variable) or the upper class limit (for a continuous variable).
2. An ogive is the graphical equivalent of a cumulative frequency distribution or a cumulative relative frequency distribution. The x coordinates of the points are the upper class limits; the y coordinates are the cumulative frequencies or cumulative relative frequencies.
3. Data that are analyzed with respect to time are called time series data. A graph of time series data is called a time series plot. The horizontal axis of a time series plot represents time (for example, hours, days, months, years). The values of the time series data are plotted on the vertical axis, and line segments are drawn to connect the points.