graphs (Statistics)

A graph in Statistics is a diagram used to display data.

A bar graph is a graph used to display discrete data.

It shows bars, with heights the same as the frequency of each category.

The bars can touch in a bar graph but generally most people put a gap between the bars to make it easier to read.

eg Number of Year 9 students born each month at ABC College

A histogram is a graph used to display continuous data, although it can be also used for discrete data too.

It shows bars, with heights the same as the frequency of each category.

The bars touch in a histogram, because the data has been placed into groups.

eg Heights of students in the form class 9WAN

A pie graph is also a graph used to display discrete data.

It is a circular graph where each sector shows the proportion of the frequency of each category.

eg Favourite subject for Year 9 students at ABC College

A stem and leaf plot (or stem and leaf graph) is a graph that displays data, usually discrete data.

It has a 'stem' which signifies the most significant figures of the data, with the 'leaves' being the remaining significant figures.

eg Mr Brown's Year 9 Algebra test results

A stem and leaf plot can be drawn back to back, with two sets of data to compare with each other.

A dot plot is a graph that also displays discrete data.

It shows dots, the number of dots is the same as the frequency of each category.

eg Siblings in Mr Brown's Mathematics class

A dot plot can also be drawn back to back, with two sets of data to compare with each other.

A time-series graph is a statistical graph that displays data (a variable) over a period of time.

It can be used to determine trends or patterns etc

eg Petrol Price Index in NZ from 2001 to 2007

A scatterplot (or scatter graph) is a statistical graph that shows any relationships between two sets of data.

It is called bivariate data (2 variables) and shows one variable on the x-axis and one variable on the y-axis.

eg Sales of ice creams vs temperature. 

Is there is relationship between how much money we sell with ice creams verses the temperature...?

A box plot (or box and whisker graph) is a statistical graph that shows 5 features of a set of data;

Lowest, Lower Quartile, Median, Upper Quartile and Highest

eg Test scores for Ms Sun's Mathematics class

A box plot can also be placed side by side to compare different data sets.