1. And Experimental Design
Scientific Method
And
Experimental Design

2. I. Steps in the Scientific Method
1. Observe around you and ask Questions
Construct a Hypothesis
-Hypotheses are educated, testable guesses based on your question
-Commonly written as ‘IF…THEN’ statements
- Variable follows IF -Expected results come after THEN
3. Set up the Experiment
4. Record and Analyze Data
5. Draw Conclusion- Does your data support or not support your hypothesis?
6. Communicate Results by graphs, tables, journals, articles, reports etc.

3. I. Setting up the Experiment
In an experiment a hypothesis is tested under controlled conditions. A control group is used for comparison because no test is performed on it, therefore using it as a ‘norm’. A good experiment only has a single variable being tested.
Independent Variable:
The variable that is changed
(What I change)
What is a Variable?
Any factor, trait, or condition that is being tested
Dependent Variable:
The variable that responds to the change made by the independent variable
(What I observe)

5. Examples: Identify the dependent and independent variables
An experiment that tests how quickly different temperatures will dissolve sugar cubes.
2. How long does it take you to get to the store?
3. An experiment that explores how various amounts of water impacts plant growth.
4. Testing the amount of fish food given to the goldfish and how big it gets over
time.

6. III. Analyzing Data Qualitative Data Quantative Data Based on judgment
And comparison
Quantative Data
Based on Numbers
Versus
Examples: Identify each as qualitative or quantitative
1. The high temperature for today is 98 degrees.
2. My cat has a green eye and a blue eye.
3. My deck was covered with water this morning so it must have rained last night.
4. I found 130 termites in the rotten log!
5. A graph showing carbon dioxide emission in Brevard for the year 2006

7. Bart believes that mice exposed to microwaves will become extra strong (maybe he's been reading too much Radioactive Man). He decides to perform this experiment by placing 10 mice in a microwave for 10 seconds. He compared these 10 mice to another 10 mice that had not been exposed. His test consisted of a heavy block of wood that blocked the mouse food. he found that 8 out of 10 of the microwaved mice were able to push the block away. 7 out of 10 of the non-microwaved mice were able
to do the same.
Identify the- 1. Control Group : Non-microwaved Mice
2. Independent Variable: Whether the mice are microwaved or not
3. Dependent Variable : Strength of Mice
4. What should Bart's conclusion be? That mice exposed to microwaves are stronger than those that are not, therefore accepting his hypothesis
5. How could Bart's experiment be improved? Larger Sample Size, Different Tests of Strength, Repetition

8. In order to test a hypothesis we need to design an experiment
In order to test a hypothesis we need to design an experiment. The most important factors of Experimental Design are:
1) Comparison - Experiments consist of a control group and an experimental group.
- The control group is never changed, consists of constants ( factors that remain the same)
-The experimental group will be changed. However, only 1 variable is changed within that group
2) Adequate Sample Size and Diversity – Is the sample size large enough to draw a conclusion? Does it represent a diverse group?

9. 3) Time Frame – Specify how long an experiment will last, how often you will record observations/data, and is this a reasonable time?
4) Record Data – Make a data table before starting the experiment and record at constant times.
Data will then be analyzed.

10. 5) Feasibility – Is the experiment practical
5) Feasibility – Is the experiment practical? Based on the amount of time, sample, and materials needed is it possible to carry out the experiment?
6) Replication – Will others be able to repeat your experiment, by following the exact procedure, to come up with similar results?