1. Scientific Method & Experimental Design
Problem/Purpose
Hypothesis
Experiment
Controls
Variables
Constants
Materials
Procedure
Data and Observations
Analysis
Conclusion
Theory

2. Do plants need food to grow?
Problem/Purpose
Do plants need food to grow?
Identify what it is you want to investigate, usually based on something you’ve observed.

3. Hypothesis what you think will happen
If a plant is given more food, then it will grow taller than if it is given no food at all
what you think will happen
a testable explanation for an observation
often given in the
“If…… then…..” format

4. Experiment the controlled test of a hypothesis contains: constants
control group
variables

5. Experiment
Sayda wanted to test the effects of different kinds of fertilizer (food supplement) on plant growth. She created an experiment using 4 plant setups, each containing 5 plants. All plants are the same kind and age, and they have all been planted in 1 kilogram of the same potting soil. Each plant in every group is given 500 milliliters of water daily and exposed to 8 hours of sunlight.
Group 1 is given 10 grams of plant fertilizer
Group 2 is given 5 grams of plant fertilizer
Group 3 is given 20 grams of fertilizer
Group 4 is given no fertilizer at all.
The height in centimeters of each plant is measured and recorded every 5 days.

6. Experiment
Now, write out in words what you think is going to happen by finishing the statement started for you.
If plants are given _____________ fertilizer, then after 15 days they will be _________________ than plants receiving different amounts of fertilizer.
Suggested answer:
If plants are given more fertilizer, then after 15 days they will be taller than plants receiving less fertilizer.

7. Experiment Set-up of controlled experiment: Group 1 Group 2 Group 3

8. Experiment
The results after 15 days:
Group 1
Group 4
Group 2
Group 3

9. Experiment constants- things that are the same for all groups
What were the constants in Sayda’s experiment?
Suggested answer:
“All plants are the same kind and age, and they have all been planted in 1 kilogram of the same potting soil. Each plant in every group is given 500 milliliters of water daily and exposed to 8 hours of sunlight.”

10. Experiment control group Suggested answer:
serves as a standard of comparison
contains all constants but not the variable
the group you don’t change from the natural condition
What was the control group in Sayda’s experiment?
Suggested answer:
“Group 4 is given no fertilizer at all.”

11. Experiment
variables
This word comes from the word “vary”, which means change or different.
For example, you could say the colors in the flowers vary from bright red to pale yellow.

12. Experiment
dependent variable- what the scientist or experimenter is testing for/measuring; what is observed and recorded
goes on Y axis
independent variable- what the scientist or experimenter changes in the experiment
goes on the X axis

13. Experiment

14. Experiment What was Sayda measuring/testing for in the experiment?
that is the dependent variable
What was Sayda manipulating/changing in the experiment?
that is the independent variable
Suggested answer:
dependent variable = height in centimeters
independent variable = amount of fertilizer

15. Materials and Procedure
materials- what you use to conduct the experiment
What are the materials used in Sayda’s plant experiment?
Suggested answer:
20 plants
20 pots
20 kg potting soil
tap water (500 mL per plant per day)
source of sunlight
metric ruler
175 grams fertilizer
electronic balance

16. Materials and Procedure
procedure- a logical order of steps to follow in solving the problem
often listed as numbered steps.

17. Data and Observation what happened during the experiment
involves all 5 senses (when safe to touch, taste or smell), otherwise we rely on sight and sound
can be qualitative- observations that are not measured
Examples: color, smell, taste, texture
can be quantitative- observations that are measured
Examples: temperature, mass, height, volume

18. Data and Observation includes the results in the form of data
data should be included as charts, tables and graphs
make sure all data tables have a title and axes are descriptively labeled
Table 1. The effect of the independent variable on the dependent variable
Independent variable (x)
Dependent variable (y)

19. Analysis
the part of an experiment where you decide what the data means (comes from the word analyze)
graphs are one tool used to analyze data

20. Analysis Graphing Guidelines:
Include a title indicating variables (what exactly does this chart show the reader).
Label the X and Y axis including units.
DRY- Dependent/Responding variable on Y-axis
MIX- Manipulated/Independent variable X-axis

21. Amount of fertilizer (g)
Graph 1. The Effect of Fertilizer Amount on Plant Height
Group 1
Group 2
Group 3
Group 4
O in.
2 in.
4 in.
6 in.
8 in.
10 in.
12 in.
14 in.
Plant growth (cm)
Amount of fertilizer (g)

22. Conclusion addresses the hypothesis
shows that the data supports or disproves your hypothesis
makes a clear relationship between the problem and results

23. Theory theory- unifying explanation for a broad range of observations
in everyday use, we say “theory” when we mean we are guessing what happened or why something happened
IN SCIENCE, theories are “the facts as we know them”; know scientific theories are based on natural and physical phenomena and are capable of being tested by multiple independent researchers; scientific theories are well-established and highly-reliable explanations

24.                      
Smithers thinks that a special juice will increase the productivity of
workers. He creates two groups of 50 workers each and assigns
each group the same task (in this case, they’re supposed to staple
a set of papers). Group A is given the special juice to drink while
they work. Group B is not given the special juice. After an hour,
Smithers counts how many stacks of papers each group has made.
Group A made 1,587 stacks. Group B made 2,113 stacks.
Identify the:
Control Group
Independent Variable
Dependent Variable
What should Smithers' conclusion be?
How could this experiment be improved?

25. Suggested answers:
Identify the:
Control Group Group B - water
Independent Variable type of drink
Dependent Variable number of stapled sets of papers
What should Smithers’ conclusion be? The special juice slows down, not speeds up, works when stapling papers
How could this experiment be improved? * same breakfast & lunch
*regulate the amount of caffeine
*measure the amount of juice
*count stapling rate before the juice for both groups and do a percent increase

26.                      
Homer notices that his shower is covered in a strange green slime.
His friend Barney tells him that coconut juice will get rid of the green
slime. Homer decides to check this out by spraying half of the shower
with coconut juice. He sprays the other half of the shower with
water. After 3 days of “treatment” there is no change in the appear-
ance of the green slime on either side of the shower.
What was the initial observation?
Identify the- Control Group
Independent Variable
Dependent Variable
What should Homer's conclusion be?

27. Suggested answers:
What was the initial observation? Green slime in the shower
Identify the:
Control Group half sprayed with water
Independent Variable type of cleaning solution
Dependent Variable amount of green slime “killed”
What should Homer’s conclusion be? Coconut juice does not work to remove green slime