Statistics: Graphs and Charts

Learn easily with Video Lessons and Interactive Practice Problems

Introduction

To display large amounts of data, the use of graphs and charts can make the information easier to view and interpret. To display data, there are many graphs and charts available. Select the most appropriate graph or chart to convey the information effectively.

Bar Graphs and Histograms

For data that is organized into different groups or categories, bar graphs or bar charts are most often used to display the information.

This graph displays the number of students per grade in a middle school.

grades

A histogram is similar to a bar graph. They both use bars to represent data, but the bars displayed in histrograms represent numerical ranges rather than just one value. Histograms are a good choice to represent information that is continuous in nature such as elasped time or age.

This histogram makes it easy to interpret the information about the age range for movie goers.

movies

Line Graphs

For information that changes over time such as height and weight, line graphs also known as line charts are an effective format to display the data.

To create a line graph, plot data points then connect with a line.

weight

Circle Graphs

Circle graphs are also called pie charts. Use this type of graph to compare the relative size of information. Each pie slice or sector represents a percentage of the circle.

From this pie chart, it is easy to interpret that pumpkin pie is the most popular of the five pies listed.

cakes

Frequency Tables and Dot Plots

Frequency tables and dot plots are often displayed together. Frequency Tables like the name implies displays the frequency of data values. Tally marks or numbers may be used to represent the frequency of data, and the information is shown in ascending order.

Dot plots are graphs that represent the information displayed in frequency tables. The advantage of dot plots is they are easy to read.

This dot plot makes it easy to see that only one player scored zero goals.

goals

Stem-and-Leaf Plots

Stem-and-leaf plots show information listed in a table. Each data value is split into a stem and a leaf. Stems, shown vertically, help to organize data into groups and the leaves, shown horizontally, provide information about individual scores within the relevant group.

Using a stem-and-leaf plot to display a student’s test scores, it is easy to conclude that most of the scores are in the 80s.

$\begin{array}{l|l} \mathbf{STEM} & \mathbf{LEAF} \\[0.5mm] \hline&\\[-3mm] \mathbf{5} & 9\\[0.5mm] \mathbf{6} & 2\\[0.5mm] \mathbf{7} & 3\\[0.5mm] \mathbf{8} & 1 \ 2 \ 2 \ 3 \ 5 \\[0.5mm] \mathbf{9} & 2\ 3 \ 4\\[0.5mm] \end{array}$