Scientific Method and Experimental Design
Name ________________ Date _____2013
1. Watch this video on the Scientific Method and take notes on the experimental design:
http://www.youtube.com/watch?v=GKGtkzgKfkc&list=PL4275A5DE33B0E496
a. Research Questions –
b. Hypothesis –
c. Independent variable –
d. Dependent variable –
e. Controlled variables (constants) –
f.
Control group -
2. Read the following descriptions of experiments. Identify for each experiment:
(1) independent variable(s) – underline once
(2) dependent variable(s) – underline twice
(3) control group – put parentheses around (or write one if not included in experiment)
(4) constant(s) - circle
(5) Write a hypothesis
A. Leah read that bees were attracted to certain colors and wondered if crickets also had a color preference. She
divided an aquarium into three sections containing different-colored dishes (red, blue, yellow) and put 2 grams
of mustard seeds in each dish. She place 30 crickets into the aquarium. She observed the number of crickets in
each section at the end of 30, 60, 90, and 120 minutes. She recorded the mass of the mustard seeds consumed
at the end of 120 minutes. She was careful to place the aquarium so that the amount of light was equal
throughout the aquarium.
Hypothesis: _____________________________________________________________
_______________________________________________________________________
B. Joan read that the gas company was burying sheets of magnesium next to pipelines to prevent rusting. She
decided to investigate the effectiveness of various metals in preventing rusting. She placed the following into
for separate test tubes of water:
1. iron nail
2. iron nail wrapped with magnesium strip
3. iron nail wrapped with copper strip
She used the same amount of water, equal amounts of the metals, and the same size iron nails. At the end of five
days, she recorded the amount of rusting and the color of the water.
Hypothesis: _____________________________________________________________
Mr. Luis A. Velazquez
_______________________________________________________________________
3. Review the Scientific Method below. Not all science is done in this way, but it is one approach that we will use in
class this year.
Research Idea
Ideas come from observation, reading scientific articles,
and many other sources.
Research the Literature
Researching the topic tells us what is known and what is
not known. This can lead to a research question to study.
Research Question
Experiment
Analyze Data
Draw Conclusions
Publish
Next Question
After we have a research question, more research can
lead to a better, more refined question.
Good Experimental Design is important in order to get
meaningful answers. (See experimental design below.)
What are the data trying to tell you? Are there patterns?
Did the independent variable really affect the dependent
variable?
Why did the independent variable affect the dependent
variable (or not)? Knowledge of the subject will help us here.
Scientists share their findings.
Learning something usually leads to more questions.
These can then be used to study the subject further.
4. What is the value of doing research on what is already known? (You will need at least 3-4 sentences to answer
this completely.)
Mr. Luis A. Velazquez
5. Create an experimental design with ONE independent variable (called a controlled experiment) for the following
research question.
RESEARCH QUESTION
What is the relationship between the amount of homework given and students’ test grades in Honors
Biology classes?
HYPOTHESIS
This is the predicted outcome. Write it in the form of a statement. (Example: Plants exposed to country music will
grow taller than plants exposed to classical music or no music.)
INDEPENDENT VARIABLE
What the scientist changes. What I put IN to the experiment. (Example: type of music)
Experimental groups:
Different levels or values of the independent variable (Example: country music, classical music, no music)
Control group:
Which experimental group is the most common? What will the scientist compare the results to?
(Example: no music)
DEPENDENT VARIABLE
What will the scientist measure? How? In what units? (Example: The height of each plant in cm after 20 days)
IMPORTANT CONSTANTS
Things that will be the same in EVERY trial (be sure not to include the independent variable here). (Example: type of
plant, amount of light and water, temperature, humidity, type and amount of soil)
Mr. Luis A. Velazquez
6. Calculate the means (averages) in the data table below. Graph the means of the data. Be sure to include a title,
labels for the x- and y-axes, and a label for each bar.
Average % test
grades
Trials
1
2
3
4
5
Mean (average)
Mr. Luis A. Velazquez
Minutes of homework per class
10
88
87
85
82
83
30
94
93
98
92
98
60
99
97
99
92
98