Graphs for Integrated Science Why use a graph? What kinds of graphs are there? How does one make a graph?

Why use a graph? Graphs communicate information visually Graphs tell a story – Show patterns and trends Not language dependent Used in newspapers, magazines and businesses around the world

What kinds of graphs are there? Three types used in integrated science Bar graphs: a graph drawn using rectangular bars to show size of a value Line graphs: a graph that uses points connected by lines to show how something changes in values Pie Charts: percentage data is shown a circle divided like pie pieces.

Bar Graphs Bar graphs help compare categories Usually independent variable (factor that differs from group to group) make up categories Categories placed upon horizontal axis Categories often qualitative or discrete values

Line Graphs Line graphs help show relationships and predictable laws Data is quantitative Values are continuous Dependent variable is on y axis Key or legend necessary if more than one line

Pie Charts Show percentage data Data is quantitative Usually has key/legend to identify categories Doesn’t use distinguish type of variable

Parts of a graph Title: Appears at the top and describes the graph Axes with labels: Reference line drawn on a graph to show values; usually one vertically (y) and on horizontal (x); define the data graphed; (axis is singular) Scale: uniform tic marks (or categories) that show the value of each interval or square; every square must equal the same amount. Legend/Key: chart to help identify different trials or parts of experiment

Parts of a graph Descriptive TITLE SCALE: tic marks (or categories) are uniformly incremented Note: this graph does not start at 0,0 but starts at (1,0) as the first data is day 1, temp 43. AXES Labels Independent variable x-axes Dependent variable y-axes

What kind of graph should I use? Line or bar? Look at the table of your results: If this column (Independent data) has Only certain fixed values, or qualitative categories, use a bar-graph: A continuous range of values, use a line-graph:

How do I make a line graph? 1. Draw in the axes and use simple scales. Put the dependent variable on the vertical y-axis Put the independent variable on the horizontal x-axis

How do I make a line graph? Draw in the axes and choose simple scales. To find a scale, Find the range (highest value – lowest value) Divide the range by the number of squares Choose the closest simple values: 1 large square = 1 centimeter (1 cm) or 1 large square = 2 cm, or 5 cm, or 10 cm Never choose an awkward scale, like 1 square = 3 cm or 7 cm Make tic marks and label the axes

How do I make a line graph? Plot the points neatly. To mark the point, use an X x Usually you need 5 or more points for the graph. x x x x x Re-check each one before your next step.

How do I make a line graph? Draw the “best fit line” If the points form a straight line… …draw the best straight line through them If the points form a curve, …draw a free-hand curve of best fit

How do I make a line graph? Check Outliers If a point is not on the line, then it is “an outlier.” Check your equipment & data Title the graph using descriptive words Use words that tell the reader what the graph is about. For example, “World population growth since 1900.” Often you will use the dependent and independent variables in the title. Title the graph using descriptive words Use words that tell the reader what the graph is about. For example, “World population growth since 1900.” Often you will use the dependent and independent variables in the title

How do I make a line graph? In summary: Draw in the axes and choose good scales, with the dependent variable on the y-axis Plot the points carefully using an X. Draw a line of best fit using a ruler for a straight line graph, or draw free-hand for a curved graph Check outliers. Add a descriptive title to the graph

Webography Free Support for Physics for You. Web. 27 Sept. 2011. http://www.physics4u.co.uk/ Graphing Scientific Data. Web. 27 Sept. 2011. Google docs. https://docs.google.com/leaf?id=0B0BBtYfjp2PoZjVjMzgwOTktYzdiYS00ODNlLTgwNGMtN2RjNWEyY2Y4ODcz&hl=en_US "Displaying Data in Tables and Graphs." Algebra to Go: a Mathematics Handbook. Wilmington, MA: Great Source Education Group, 2000. Print.