Biology & Graphing at Bellevue CC 

Rosemary Richardson

rrichard@bcc.ctc.edu

 

Jenny Laveglia

jlavegli@bcc.ctc.edu

 

Bellevue Community College

Introduction - Data Analysis

Collecting and analyzing data are important steps in the scientific process. We need to analyze data to see how the data support (or do not support) our hypotheses.

Graphing is one method used to help us analyze data we collect. A graph is a picture that shows a relationship between two quantities. A graph can transform data in ways that demonstrate aspects of the data more clearly and meaningfully such as showing patterns and trends or summarizing information.

Good graphs explain the results of the exercise and help us pose questions and guide us to new or revised hypotheses. In order to graph well, you must be able to choose appropriate graphs for particular data sets and you need to be familiar with the language of graphing

Language of Graphing

Data - Data are pieces of numerical information. Data can be displayed in tables, in graphs, or as sets of ordered pairs. (Data is actually plural. The singular form of data is datum.)

Graph - A graph is any visual representation of a data set. It may be a pie chart, a bar graph, a line graph, or a scatterplot.

Pie chart - A pie chart is a circular graph, cut into wedges or slices. Pie charts are used primarily for data that adds to 100%. The size of each pie slice is proportional to the percentage of the category it represents.

Bar graph - Bar graphs display quantities (data) as bars that run either vertically or horizontally. The bar length corresponds to its numerical value.

Line graph - In a line graph each point represents one datum and consecutive points are connected by line segments. A line graph is often used to show how some quantity changes with time.

Group Assignment – Graphing Practice

Data for the percentage of ABO blood types among United States population cohorts is

shown below. Working in groups of no more than three students, make a bar graph, pie

chart and line graph of the data.

ABO Blood Types in the United States Population

ABO Blood Type  % of US Population
White Black Asian
A 40 27 28
B 11 20 27
AB 4 4 5
O 45 49 40
  1. Discuss the strengths and weaknesses of each of the three graphs.
  2. Which graph represents the data most effectively?
  3.  Discuss why this graph is more effective than the other graphs you made.
  4. What type(s) of data can be displayed more effectively with the types of graphs that you would not use for the blood type data?
  5. Evaluate your three graphs.
  6. Are the graphs you made excellent, good, adequate, poor? 
  7. Identify criteria you used to evaluate your graphs.

Materials for this exercise were developed at the MAC (Mathematics Across the Curriculum) 2002 Summer Institute by Jennifer Laveglia and Rosemary Richardson, Bellevue Community College, liberally assisted by Jennifer McFarland, Edmonds Community College.