Types of Graphs 

Pictograph A chart giving statistics in pictorial form. For example, using a dollar in increasing sizes to represent the increase in the purchasing power over time. 

Pie chart (Circle Graph) A circular chart that provides a visual concept of a whole (100% = 360 degrees). The pie is divided into slices, each corresponding to a category of the variable represented (e.g. each age group). The size of the slices is proportional to the percentage of the corresponding category. Each part illustrates a ratio of the whole.

Tally chart Used to record data from an experiment, count the occurrences of an event and develop frequency distribution tables. 

Frequency table A table presenting statistical data by putting together the values of a characteristic along with the number of times each value appears in the data set. 

Histogram A graph that consists of a series of columns, each having a class interval as its base and frequency of occurrence as its height. 

Class intervals If a variable has a large number of values, it is easier to present the data by grouping the values into class intervals (i.e., age of the population presented as age groups, for example 04, 59, 1014, 1519, etc.) rather than presenting all of the values together. This makes it easier to see the trends in the data. 

Bar graph A diagram that compares bars of the same width but of different heights according to the statistics or data they represent. Bar graphs are horizontal. (A vertical bar graph is called a column graph.) These show a comparison of two or more quantities. 
Double Bar graph allows more than one set of data to be compared.

Line graph A graph in which successive points representing the value of a variable at selected values of the dependent variable are connected by straight lines. These show change over time. 
Double Line graph allows two sets of data to be compared over a period of time.

Stem and leaf plot A semi-graphical method used to represent numerical data, in which the first (leftmost) digit of each data value is a stem and the rest of the digits of the number are the leaves. A stem and leaf plot shows all the data values from a sample set. 
Double Stem and leaf plot allow two sets of related data to be shown, one on each side of the stem.

Dot graph (scatter plot) A two dimensional diagram that indicates two variables as a series of dots, mainly used to show the correlation between the two variables. 

Tree diagram A branching diagram that shows all possible combinations or outcomes. 

Range The full distance over which results vary along a number line. The exclusive range is the difference between the largest and smallest results in a data set, and the inclusive range is the difference between the upper real limit of the highest interval and the lower real limit of the lowest interval.