Graphing & Statistics Honors Biology 2008-2009

Importance Provide a lot of information in a small amount of space. Represent information at a glance Replace the need for lots of words in a given context Honors Biology 2008-2009

Graphs vs. Charts Graphs are used to show trends in data Tables are used to show exact values of the data Honors Biology 2008-2009

Types of Graphs 1) Pictograph- A graph used to compare data using symbols or graphics. Honors Biology 2008-2009

Types of Graphs 2) Pie Chart- A graph used to compare parts of a whole. Honors Biology 2008-2009

Types of Graphs Bar graph – A graph using parallel bars or rectangles to compare information When you can break your data into distinct groups Non-continuous data Honors Biology 2008-2009

Types of Graphs Line graph- A graph comparing two variables that are plotted on a horizontal and vertical axis. Usually used with continuous data, i.e. time Honors Biology 2008-2009

Line Graphs The horizontal axis is called the “x-axis” The vertical axis is called the “y-axis” Y-axis X-axis Honors Biology 2008-2009

Creating a Line Graph Title your graph – Be specific! Place the name of the independent variable (what you’re testing) on the x-axis. Include your units! Place the name of the dependent variable (what you’re measuring) on the y-axis. Include your units! Name of Graph Dependent Variable Independent Variable Honors Biology 2008-2009

Use Appropriate Scale Using real graph paper, draw your scale (distances between grid spaces) on your axes. Make them big enough so that you can see your data comfortably. 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 10 11 Honors Biology 2008-2009

More on Scale Your scale should cover the ranges of your data set. It does not have to start at 0 Honors Biology 2008-2009

Draw A Best Fit Line Graph all of the points for your dataset or table. Draw a “best fit” line (linear regression) between them. Drawn as an average between all the points shown. Honors Biology 2008-2009

Add A Figure Caption Figure captions (placed below the figure) contain the details of what the figure represents. For instance, a caption for the tree growth data might tell how many replicates were done, that the trees measured were from a open field, how long the trees grew for, etc. Tables have titles (placed above the Table). A title is a relatively brief description of the table. Honors Biology 2008-2009

Statistical Analysis on data sets Mean - the average value of your data set. Example: 2,4,3,2,4,3 What is the average? 2. Median - the middle value in your data set Arrange data in increasing (or decreasing) order. Odd number of data points = use value in middle Even number of data points = use the value half-way between the two center points. Example: 3,8,4,1,7,4,3,9,6,4,8 3. Mode (fashion) - the most common value in your data set Can have more than one Not always representative of the data 4. Range - the difference between the largest number and the smallest number in the group. Example: 1,3,8,6,8 8 is the largest and 1 the smallest number Hence range is 8-1 = 7 Honors Biology 2008-2009