Distribution Graphs

Also known as a probability distribution
A probability distribution shows all the possible outcomes and what the probability is for each of them.

It is possible to convert a frequency table, frequency polygon or histogram into a probability distribution.
The absolute frequencies need to be converted into relative frequencies.
To do this sum all the frequencies from all the intervals and then divide each interval frequency by the total frequency and multiple by 100 to get the percentages.
These new relative frequencies can then be plotted to create a relative frequency polygon.

Column Chart

A column chart is commonly used to show the frequency of discrete data
Remember that discrete data is counted (not measured)
These values are usually grouped by category
There will often be spaces between the columns
The columns can be rearranged or reordered without a loss of meaning
All the columns have the same width

Histogram

A histogram is commonly used to show the frequency of continuous data.
Remember that continuous data is measured (not counted)
These values are grouped into equal size intervals (classes or bins)
There are no spaces between the columns.
The columns cannot be rearranged or reordered
All the columns are not always the same width

These column charts (or histograms) are often converted to (absolute) frequency polygons by connecting all the midpoints with a straight line.
The reason for using the midpoint is to make sure that the surface area of the frequency polygon is the same as the original column chart
These dots and lines produce the shape of the frequency distribution
If more than one data set is displayed on the same chart, it is called a combined absolute frequency polygon.

Tally Chart