Introduction to
SCIENCE
And the
SCIENTIFIC
METHOD
What is science?
The goal of science is to investigate and
understand the natural world, to explain
events in the natural world, and to use those
explanations to make useful predictions
• Science deals only with the natural world.
• Scientists collect and organize
information in a careful, orderly way,
looking for patterns and connections
between events.
• Scientists propose explanations that can
be tested by examining evidence.
• Science is an organized way of using
evidence to learn about the natural
world.
How is science done?
Science begins with an observation.
•
This is the process of gathering
evidence of
an event or
process in a careful, orderly
way.
Data is the information gathered while
making observations.
There are TWO types of Data…
Quantitative:
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Data in numbers that is obtained by
counting
(How many? How tall? How far?)
Qualitative:
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Data that describes what you are observing.
Cannot be counted.
Hypothesis
• A Hypothesis is a scientific explanation for a
set of observations
• A hypothesis must be stated in a way that
makes it “testable”. The hypothesis is just a
possible answer to a question, and it must
be thoroughly tested.
The Scientific Method
The scientific method is a series of steps
used by scientists to solve a problem or
answer a question.
Steps:
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Observation/ask a question
Form a hypothesis
Design a controlled experiment
Collect and Analyze Data
Form a conclusion
Step 1: Observe/Ask a Question
A problem or question must first be identified
• Does heat affect heart rate?
• Why do plants bend towards light?
• What kind of fertilizer makes plants grow tallest?
Step 2: Form a Hypothesis
A possible explanation to a question or problem
• It is simply a prediction that has not yet been proven or
disproven
• It must be stated in a way that is testable. It is considered
“testable” if evidence can be collected that does, or does not
support it.
Step 3: Design a
controlled experiment
• The factors in an experiment that can be changed are
called variables.
• A controlled experiment works with ONE variable at a
time.
• An experiment is based on comparing a “controlled”
group to an “experimental” group.
1)These two groups are identical except for one factor
2) The control group serves as the comparison. The factor you
are testing for remains unchanged.
3) The experimental group shows the effect of the variable
being tested.
Example:
You want to see what concentration of fertilizer will make a
plant grow the tallest. One plant receives no fertilizer, one
receives a low concentration, once receives a medium
concentration, and the fourth receives a high concentration.
Describe the control group: The plant that receives NO fertilizer
Describe the experimental group: The three plants receiving
varying amounts of fertilizer
What variables are kept constant? Amount of water, light,
container size, soil type
What variables are changed? The concentration of fertilizer
There are TWO variables in an
experiment:
Independent Variable
• The variable deliberately changed by the scientist
Dependent Variable
• What is observed during the experiment. This is our data
from the experiment, resulting from what was changed.
In the above experiment, what was the independent
variable?
What was the dependent variable?
Step 4: Recording and
Analyzing Results
• The data that has been collected must be organized
and analyzed to determine whether the data is reliable.
• Does the data support, or not support the hypothesis?
Step 4: Recording and
Analyzing Results
Make a data table and graph of your results
When graphing:
Independent Variable is on the X-axis
Dependent Variable is on the Y-axis
Step 4: Recording and
Analyzing Results
Step 5: Drawing Conclusions
• The evidence from the experiment is used to determine
whether the hypothesis is proven or disproven.
• Experiments must be repeated over and over. Results must
remain the same for a valid conclusion to be reached.
Forming a Theory
• A theory is a broad and comprehensive statement
of what is thought to be true.
• A theory is supported by considerable evidence.
• A theory may be formed after the hypothesis has
been tested many times and the results have
remained the same.
Practice Problem
You are testing a new headache drug with 100
participants. You want to know what concentration
of the drug will be most affective at curing
headaches. You have the following materials:
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100 participants
25 pills with 25% drug concentration
25 pills with 50% drug concentration
25 pills with 75% drug concentration
25 pills with 0% drug concentration (placebo)
• What is your hypothesis?
• What is your control group?
• What is your experimental group?
• What is your independent variable?
• What is your dependent variable?
Control Group
Experimental Group
The 25 participants taking
the pills with 0% medicine
are the control group. They
should not be affected by
their pills.
The participants taking pills
with varying concentrations
of medicine are the
experimental group. They
should be affected by their
medicines in different ways.
The independent variable is the concentration
of the drug in the pill
In a controlled experiment, all variables must
be kept constant except those deliberately
being changed by the scientist.
What variables must be kept constant in this
experiment?
• Time of day the pill is taken
• Type of fluid the pill is taken with
• Lifestyles of participants should be similar
After 30 days of participants taking the experimental
drug the following results were obtained:
0% Pill: Headaches 6-7 days a week
25% Pill: Headaches 3-4 days a week
50% Pill: Headaches 1-2 days a week
75% Pill: Headaches 0-1 days a week
Conclusions:
• Did these results prove or disprove your hypothesis?
• What is your conclusion based on these results?
Why is it important to have a large sample size
in any experiment?
It is important to test a large sample in order to
get a true picture of the results of the
experiment. If the sample size is too small, an
inaccurate conclusion may be reached.
Results obtained by testing a large number of
individuals would be much more accurate
than if only a few individuals had been tested.
Why is it important to repeat an experiment
many times?
Repeating an experiment is important to see
that you get the same results each time. This
gives validity to the test results.
What is the importance of the control?
The control group shows us what will happen when the
experimental factor is omitted. Without the control,
there would be no basis for comparison, and you
wouldn’t know how the experimental group was
effected.
How is a theory different than a hypothesis?
A hypothesis is an educated guess that is
testable through observation and
experimentation. A theory is a broad
statement about what is believed to be true
based on experimentation and data.
Why is it important for a scientist to carefully
record ALL of their procedures?
• All experiments should be repeatable by another
scientist.
• This allows them to verify if the original results were true.
What is the difference between the
independent and dependent variable in an
experiment?
• The independent variable is the variable deliberately
changed by the scientist.
• The dependent variable is what is affected by the change.
This is what you are measuring.
In a controlled experiment, why must all variables be
kept constant except for the one you choose to
change?
• Because if you did not keep all other variables
constant, you would not know what was responsible
for the results you were observing.
Questions
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