Data Representation: Making Tables & Graphs

Data Tables

Why create data tables? To neatly and logically organize data from an experiment To make data collection during an experiment easier

A Typical Data Table

Why construct a graph? To create a picture of the data gathered during an experiment To compare data from control and experimental groups To determine trends of data: increase, decrease, or stay constant

Line, Bar or Circle? What Type of Graph?

Adapted from Miller & Levine Biology Graphing: Line, Bar or Circle? Appendix A discusses tables and graphs as basic science skills. Review the best type of graph in each scenario. _________________ graphs are typically employed to display data that shows how the dependent variable changes in response to changing the independent variable. _________________ graphs are best when displaying data that falls into separate categories and when the data all the categories for a single group are given. _________________ graphs are commonly used when comparing data from two or more categories.

Line Graphs Shows how dependent variable (D.V.) changes in response to manipulation of independent variable (I.V.) Can be used when I.V. is continuous Allows you to estimate values for conditions you did not test Smooth curve vs. Best Fit

To construct a line graph, follow these steps. 1.On graph paper, draw a horizontal, or x-axis, and a vertical, or y-axis. 2.Label the horizontal axis with the name of the independent variable. Label the vertical axis with the name of the dependent variable. Include the units of measurement on both axes. 3.Create a scale on each axis by marking off equally spaced numbers that cover the range of the data values collected. 4.Plot a point on the graph for each data value. To do this, follow an imaginary vertical line extending up from the horizontal axis for an independent variable value. Then, follow an imaginary horizontal line extending across from the vertical axis at the value of the associated dependent variable. Plot a point where the two lines intersect. Repeat until all your data values are plotted. 5.Connect the plotted points with a solid line. Not all graphs are linear, so you may discover that it is more appropriate to draw a curve to connect the points.

Bar Graphs Useful for comparing data from two or more distinct categories

Circle Graphs Display data as parts of a whole Bar graph comparison: Same: data falls into separate categories Different: must have data for all the categories (100%)..circle or pie

How to make the perfect graph: 1.Assign variables to each axis --> Independent variable on x-axis (UNITS) --> Dependent variable on y-axis (UNITS) --> Make sure each variable has units in ( ) 2.Set a scale for each axis (see following instructions)

Step One: Develop a scale Find the largest number in each data set. The largest number is important because it is the maximum value you need have on the axis. Set a scale for each axis

Step Two: Analyze your graph paper Count the number of spaces along each axis. 8 spaces 4 Remember your largest number from step one?…The last number on each axis must match or be slightly larger than the largest number in the data set Set a scale for each axis

8 spaces Step Two: …..continued Looking at the X axis the value between each space must be exactly the same... (this is called the space size) AND we must reach 210 or go a little (not much) over didn’t work…. how do you find the magic number? Don’t just guess But this won’t work Set a scale for each axis

Step Three: Finding the space size  How to find the magic number or space size!  Divide the largest # in the data by the number of spaces (round up*) 8 spaces ÷ 8 = or Set a scale for each axis

Step Four: Mark the scale on the graph  Start with lowest # in your data set  Multiply the line # times 27 (space number) 4 Your last number should match or be slightly larger than the highest number in your data set Set a scale for each axis

Y Axis: Repeat Steps 3 & 4  Find the space size  Mark the scale on the graph 4 Move on to Step spaces 45 ÷ 8 = Set a scale for each axis

Step Five: Plot the data Use the data sets to plot the coordinates Check your work! Set a scale for each axis

How to make the perfect graph: 3. Plot the data set (or sets) --> Use a shape for each data point --> Use different shapes for each data set plotted on graph --> Make a key to identify each data set plotted on the graph

How to make the perfect graph: 4. Draw a line -->Connect the dots or “line of best fit” ? -->Straight line or curve?  Line graph or bar graph? -->Use a ruler to draw lines

How to make the perfect graph: 5.Title the graph -->Use both variables in your title; be specific! -->Write neatly at the top of the graph -->Use proper format: Effect of (independent variable) on dependent variable OR Effect of (x-axis) on (y-axis)