1. Experimental Design and the Scientific Method
Life Savers Lab

2. However, science involves a series of common steps...
There is
NO SINGLE METHOD
for doing science!!!!
However, science involves a series of common steps...

3. Steps of the Scientific Method
1. Make an Observation
Example:
It takes students differing amounts of times to eat a Life Savers.

4. Steps of the Scientific Method
2. Ask a Question
Examples:
Does flavor influence how long it takes to eat a Life Savers?
Does gender affect how long it takes to eat a Life Savers?

5. Steps of the Scientific Method
3. Form a Hypothesis and …
4. Make a Prediction
Hypothesis: A proposed explanation that answers your question.
This must be TESTABLE!
Statement: If_________, then_______
Prediction: A statement that forecasts what would happen if your hypothesis is true.

6. Steps of the Scientific Method
5. Test your hypothesis
Experiment: An investigation that tests your hypothesis under controlled conditions.
Experimental Design: How you set up your experiment.

7. Experimental Design
Control Group = you use the control group data to compare to your experimental group data
Experimental Group = the group that is being tested on

8. Experimental Design Cont.
Constant = Anything that stays the same during an experiment (ex: same flavor, same stop watch, etc)
Controlling your experiment ensures that extra independent variables can’t sneak in and affect your data
Independent Variable = It affects the dependent variable. This is the variable that you change.
Ex: Color of lifesaver, Flavor of lifesaver
Dependent Variable = It depends on the independent variable. This is the variable you measure.
Ex: the length of time to consume a lifesaver

9. Experimental Design Cont.
Let’s say you have 2 variables and you can’t tell which should be the dependent variable and which should be the independent variable
We know that the dependent variable depends on the independent variable
Put the variables into this sentence and see if it makes sense “______ depends on ______”
Which sentence makes more sense?
“Temperature depends on the Number of Sharks.”
“The Number of Sharks depends on Temperature.”
Temperature (C)
Number of Sharks 15 22 18 20 16

10. Steps of the Scientific Method
6. Analyze Data and Draw Conclusions
Qualitative Data = Deals with descriptions. Observed, but not measured.
Ex: color changes to the lifesaver as you consume it
Quantitative Data =Deals with numbers, can be measured
Ex: The number of seconds needed to consume a lifesavers
Hint: Think “N” for NUMBER!

11. Qualitative or Quantitative?
(pay attention but you don’t have to write this down)
The table surface is smooth
Qualitative
The peanut weighs 1.75 g
Quantitative
The leaf is dark brown
There are 15 flowers with white petals on them

12. Graphing Guide Some rules to follow….
Graphs are an easy way to display your data.
Which graph you use depends on what data you have.
Bar Graph
Pie Graph
Line Graph
(Comparing trends & changes)
(Comparing parts of a whole)
(Comparing groups)

13. Graphing Guide Cont. Always remember to title your graph.
Independent Variable always goes on X-axis (horizontal).
Dependent Variable always goes on Y-axis (vertical).
Label the X and Y axis.
When graphing, use the “Dry-Mix” to help you remember. Dependent – Responding –Y axis Manipulated – Independent – X axis. This will insure that all of your labels are correct!

14. Practice James wants to perform an experiment
(If we are taking the time out of class to work on practice problems together it is in your best interest to follow along because you might see something similar on an upcoming assessment!)
James wants to perform an experiment
testing how long it takes his dog Spot to eat
3 different brands of dog food.
What is the independent variable?
What is the dependent variable?

15. Practice Cont.
James records that Spot finishes Brand C in the least amount of time, James then concludes that Spot must like Brand C dog food the best.
What is the observation?
What is the inference?