1. EXPERIMENTAL DESIGN AND THE SCIENTIFIC METHOD

2. Graphs
We will use various graphs when we analyze and conduct experiments in class
You will also use graphs as a visual way to show data
When you take Biology, you will be expected to know what each part of a graph means and how to answer specific questions using data from a graph

3. 3 Main Types of Graphs Bar Graph Line Graph
Pie Graph (often called a pie chart)

4. Bar Graph
Use a bar graph when comparing Qualitative Data (categories) and numbers
For Example: Number of each color car in the parking lot

5. Pie Graph Use pie graphs when looking at percentages of a whole
For Example: What percentages of each element make up the earth’s crust?

6. Line Graph
 Use line graphs when comparing two types of Quantative data (two sets of numbers)
For Example: Amounts of water (mL) effects on plant height (cm)

7. ( what you are measuring) (what I change in the experiment)
Parts of a Graph
Dependent variable (on Y-axis)
Independent variable (on X-axis)
Title (IV versus DV)
Numbers of measurement in eve n increments
( what you are measuring)
Dependent Variable
Independent Variable
(what I change in the experiment)

8. Draw This Diagram!

9. 1—OBSERVE!!!
Make observations about the world around you—this is what scientists do and this leads to a question
Example: My grass isn’t growing.

10. 2—QUESTION???
Form a question about something you want to know about. (typically based on the observation)
Example: Why isn’t my grass growing?

11. 3—HYPOTHESIS
This is an educated guess as to the answer to the question
“If…,then…”
MUST be testable
Does NOT start with “I think…”
Example: If part of the grass is watered and part is left unwatered, then the watered part will grow more.

12. 4—TEST YOUR HYPOTHESIS
Do an experiment—write a procedure so that someone else can repeat it
Variables--anything that can be changed in an experiment
Independent variable—the variable the experimenter is changing/manipulating
Dependent Variable—the variable that is being measured (it changes as a result of what the experimenter changed)

13. Control Group—the standard for comparison in an experiment, the group that remains the same and does not receive the IV
Replicates—test the experiment many times so that results aren’t random (also know as trials)
Constants—everything in an experiment that is kept the same to ensure the IV is what caused the outcome of the experiment (change only the IV, nothing else)

14. Example: Testing the hypothesis would be splitting lawn into 8 chunks, not watering 4 of them, and watering the other 4 with a consistent amount of water.
What would the independent variable be?
Amount of water
What would the dependent variable be?
Growth of grass/lawn
What would the control group be?
The part of the lawn with no water.

15. Example Continued…
How many trials are there? 4
What are some things that need to be held constant in an experiment?
Amt. of sunlight, amt. of fertilizer, location of grass, person watering, type of grass

16. 5—COLLECT & GATHER DATA
Observe what happened and write it down on a data table.
Average height of grass—No Water
Average height of grass--Watered 500 mL/day
Before starting
5 cm
After Week 1
6 cm
9 cm
After Week 2
15 cm
After Week 3
7 cm
23 cm
After Week 4
7.5 cm
28 cm

17. 5 (2nd part) GRAPH YOUR DATA
Create a line or bar graph to show your data
Use a line graph if both sets of data are numeric
Use a bar graph if one set is words/categories
X-axis contains Independent Variable
Y-axis contains Dependent Variable
Title must be IV vs. DV
Both axes must be labeled w/correct units
Use increasing even increments along axes

18. 6—RESULTS
Summarize what data table says in sentence form—factual information only!!! NO opinions!!!
Example: Both sets of grass began at a height of 5 cm. Not watering the grass caused an overall average growth of 2.5 cm after 4 weeks, whereas watering the grass caused an overall average growth of 28 cm after 4 weeks.

19. 7—DRAW A CONCLUSION
After looking at results, tell what the outcome of the experiment is
Support or reject the hypothesis
If hypothesis is rejected, make a new one.
Example: Watering the grass does cause the grass to grow more than not watering it. The hypothesis is supported by the data (accept).

20. TIPS/GUIDELINES
Throughout the writing of an experiment, never use personal pronouns (I, me, we, us, etc.)
When graphing, you CANNOT include any breaks!!!
No naked numbers on graphs, data tables, results, conclusions, etc.
Be as specific as possible with everything!!!
The experiment must be repeatable w/o asking questions.

21. I want to see if vinegar or water boils the fastest
I want to see if vinegar or water boils the fastest. What is the independent variable?
boiling
Speed of boiling
Type of liquid
Person testing

22. I want to see if vinegar or water boils the fastest
I want to see if vinegar or water boils the fastest. What is the dependent variable?
boiling
Speed of boiling
Type of liquid
Person testing

23. I want to see if girls or boys are better in Science
I want to see if girls or boys are better in Science. What is the independent variable?
Gender of the student
Grade earned in class
Person testing
Science Class

24. I want to see if girls or boys are better in Science
I want to see if girls or boys are better in Science. What is the dependent variable?
Gender of the student
Grade earned in class
Person testing
Science Class

25. The independent variable is graphed along the x-axis.
True
False

26. What is the scientific method?
A statement of fact.
A way to graph information.
A rigid step-by-step process.
A way to answer a question or solve a problem.

27. Why do we repeat an experiment several times?
To ensure our results aren’t random.
It’s so much fun!
That’s just the way things are.
To make the experiment testable.

28. Which of the following would be a CORRECT hypothesis?
I think Super Fertilizer will make the plants grow the tallest.
Super Fertilizer will make the plants grow the tallest.
If Super Fertilizer is added to the plants, then they will grow the tallest.
Super Fertilizer is so super, it will help plants grow tall.

29. Based on the Graph, what is the independent variable?
Plant Growth
Amount of Water cm mL

30. Based on the Graph, what is the dependent variable?
Plant Growth
Amount of Water cm mL

31. If comparing Super Fertilizer to Fertilizer X and no Fertilizer, what is the control group?
The amount of Fertilizer