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

Graphs for Integrated Science

• Why use a graph?• What kinds of graphs are there?• How does one make 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

Why use a graph?

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 GraphsBar 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 GraphsLine 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

Descriptive TITLE

AXES LabelsIndependent variable x-axesDependent variable y-axes

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.

Parts of a graph

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:

What kind of graph should I use? Line or bar?

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?

1. 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) or1 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?

2. Plot the points neatly.To mark the point, use an X

xx

xx

xx

Re-check each one before your next step.

Usually you need 5 or more points for the graph.

How do I make a line graph?

3. 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?

4. Check OutliersIf a point is not on the line, then it is “an outlier.”

Check your equipment & data

5. Title the graph using descriptive wordsUse 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:

1. Draw in the axes and choose good scales,with the dependent variable on the y-axis

2. Plot the points carefully using an X.

3. Draw a line of best fitusing a ruler for a straight line graph,or draw free-hand for a curved graph

4. Check outliers.

5. Add a descriptive title to the graph

How do I make a line 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.