1. GRAPHS IN SCIENCE

2. Drawing a graph …and when should I draw a line-graph?
When should I draw a bar-chart…?

3. Drawing a graph Look at the table of your results: If this column has
only certain fixed values,
use a bar-chart:
a continuous range of values,
use a line-graph:

4. Graphing in Science
Graph Types
Line Graph - Use when the IV changes amount (day #, amount of fertilizer, etc)
Bar Graph - Use when the IV changes type (person name, color of flower, etc.)

5. Choosing the Right Graph
Use a bar graph if you are not looking for trends (or patterns) over time; and the items (or categories) are not parts of a whole.
Use a pie chart if you need to compare different parts of a whole, there is no time involved and there are not too many items (or categories).
Use a line graph if you need to see how a quantity has changed over time.  Line graphs enable us to find trends (or patterns) over time.

6. Graph data Make the data table into a graph
Graphs make it easier to see patterns in the data.
Graphs
X-axis independent variable
Y-axis dependent variable

7. Line graph
Line Graph
Used to show changes in dependent variable (plant growth) over time.
Must have title, x-axis title (with units) and y-axis title (with units)and a legend,a short description of the data graphed.
Compare and look for trends and patterns using graphs
example

8. The Uses of Graphs
Line graphs show changes over time or the change of one variable (dependent variable) due to the change of another variable (independent variable).

9. Line Graph A line graph is used to show change over time.
It's clear to see how things are going by the rises and falls a line graph shows.

10. 5 steps in drawing a graph
1. Choose simple scales.
For example:
1 large square = 1 newton (1 N) or
1 large square = 2 N, or 5 N, or 10 N
But never choose an awkward scale,
like 1 square = 3 N or 7 N
Choose a scale that will make your graph
use most of the sheet of paper.

11. Choosing a Scale and Interval
1. Find the range for the variable Range= largest value – smallest value 2. Divide the range by the number of intervals you want…spread it out. After dividing , round to the easiest counting number (5 instead of 4.3) 3. Use the rounded number to mark off intervals along the axis.

12. 5 steps in drawing a graph
1. Choose simple scales.
Put the dependent variable on the ‘y-axis’
and
the independent variable on the ‘x-axis’

13. 5 steps in drawing a graph
2. Plot the points neatly.
To mark the points we usually use an X x x x
Usually you need 5 or more points for the graph. x x x
Re-check each one before your next step.

14. 5 steps in drawing a graph
If the points form a straight line…
…draw the best straight line through them x
‘line of best fit’
Check that it looks the best straight line.

15. 5 steps in drawing a graph
4. If the points form a curve…
…draw a free-hand curve of best fit
Do not join the points like a ‘dot-to-dot’.

16. 5 steps in drawing a graph
In summary:
Choose good scales, with the dependent variable on the y-axis
Plot the points carefully
Connect each point, if a line graph
Draw a line of best fit if it is a scatter plot using a ruler for a straight line graph, draw free- hand for a curved graph

17. Bar graph
Bar Graph
Use it when a set of measurements can be split into discrete and comparable groups
To show the relative change between these groups.
Must have titles and legend

18. The Uses of Graphs
Bar graphs show comparisons.

19. Bar Graph A bar graph is used to show relationships between groups.
The two items being compared do not need to affect each other.
It's a fast way to show big differences. Notice how easy it is to read a bar graph.

20. How to set up your graph!

21. How to set up your graph!
Y Axis
(This is for your dependent variable)

22. How to set up your graph! X Axis
(This is for your independent variable)

23. TAILS
Teachers’s Favorite Singer
T - Title

24. TAILS T - Title A - Axis Teachers’s Favorite Singer
Y Axis = Dependent Variable
X Axis = Independent Variable

25. TAILS T - Title A – Axis S – Scale
Teachers’s Favorite Singer
Decide on an appropriate scale for each axis.
Choose a scale that lets you make the graph as large as possible for your paper and data
T - Title
A – Axis
S – Scale

26. TAILS T – Title A – Axis I – Interval S – Scale
Teachers’s Favorite Singer
The amount of space between one number and the next or one type of data and the next on the graph.
The interval is just as important as the scale
Choose an interval that lets you make the graph as large as possible for your paper and data
T – Title
A – Axis
I – Interval
S – Scale

27. TAILS T – Title A – Axis I – Interval S – Scale
Teachers’s Favorite Singer
T – Title
A – Axis
I – Interval
S – Scale 25 20 15 10 5

28. TAILS T – Title A – Axis I – Interval L – Labels S – Scale
Teachers’s Favorite Singer
T – Title
A – Axis
I – Interval
L – Labels
S – Scale 25 20 15
Number of Teachers 10 5
LABEL your bars or data points
Toby Keith
Madonna
Elvis
Sting
Sinatra
Singers
Label your Y Axis. What do those numbers mean?
Give the bars a general label. What do those words mean?

29. When to use… Bar graphs Used to show data that are not continuous.
Allows us to compare data like amounts or frequency or categories
Allow us to make generalizations about the data
Help us see differences in data
Line Graphs
For continuous data
useful for showing trends over time

30. Pie chart Pie Graph When showing parts of a whole..i.e. percentages
Must have a title and a legend

31. The Uses of Graphs
Circle graphs show percentages of the whole
Coconut

32. Circle Graph or Pie Graph
A circle graph is used to show how a part of something relates to the whole.
This kind of graph is needed to show percentages effectively.