Scientific Method
Objectives
Describe the steps of the scientific method.
Differentiate between the independent and dependent variables, and define
th control variables that need to be considered in a given experiment.
Use the scientific method to investigate an ecological problem related to your
campus.
Scientific method
Scientific information is acquired by a
process know as the scientific method.
The scientific method involves a series
of steps:
Observation
Problem
Hypothesis
Experiment
Data
Conclusions
Observation
Observation involves gathering
information as well as studying
previous data.
Scientists use all of their senses to
make observations (sight, smell, taste,
touch, sound).
They also use instruments like the
microscope and take advantage of the
past work of other scientists.
Problem (asking the question)
Making observations leads to
questions.
Scientists only consider questions that
can be answered by experimentation.
Moral and religious beliefs are not
testable scientifically.
The problem should be a question
asking how one variable affects
another.
Hypothesis
The hypothesis is a testable statement
that tells how you believe one
variable will affect another, based
on input from various sources.
The hypothesis is usually expressed as
a prediction with an if…then
format.
State your hypothesis in a way that
can be easily measured and that
will help answer your original
question.
Variables
A variable is any factor, trait or condition that can exist in
different amounts or types.
An experiment usually has three types of variables:
the experimental or independent variable
the response or dependent variable
Experiments also have controlled variables.
Controlled variables can affect the dependent variable
and therefore must remain constant.
Most experiments have more that one controlled variable.
The Independent and Dependent
Variables
Independent variable
Dependent variable
Is the variable being tested.
Is the variable that changes in
response to the independent
variable.
It is the variable that can be
manipulated by the scientist.
It is also called the experimental
variable.
It is also called the response variable.
Experiment
Testing your hypothesis involves either
conducting an experiment or
making further observations.
The experiment should have a control
group or control which goes
through all the steps of an
experiment but lacks the variable
being tested.
Data
The results of an experiment are referred to as the
data.
Data should be observable and objective rather that
subjective or based on opinion.
Mathematical data are often displayed in the form of
a graph or table.
The larger the sample size, the larger the effect,
the less likely that the result is due to chance.
Statistical tests are used to evaluate how likely the
results are due to chance.
Conclusion
Scientists analyze the data in order to
reach a conclusion.
The conclusion states whether the
results of the experiment support
or reject the hypothesis.
Experiments and observations must be
repeatable (get the same results).
An example of using part of the
Scientific Method
Question
(problem)
How much water flows through a faucet at different
openings?
Independent variable Water facet opening (closed, half open, fully open)
(what I change)
Dependent variable
(what I observe)
Amount of water flowing measured in liters per min.
Controlled variables
(what I keep the same)
The faucet
Water pressure
Hypothesis
If I open the faucet, then it will increase the flow of water.
(If __(I do this)__, then
___(this)__will
happen.
Scientific Method Activity: Problem 1
Question
(problem)
Independent
variable
(what I change)
Dependent variable
(what I observe)
Controlled variables
(what I keep the
same)
Hypothesis
(If __(I do this)__,
then ___(this)__will
happen.
Does heating a cup of water allow it to dissolve more
sugar?
Scientific Theory
The ultimate goal of science is to understand the natural world in terms of
scientific theories.
Scientific theories are concepts that join together related and well-supported
hypothesis.
A theory is supported by a broad range of observations, experiments and data.
Basic Theories of Biology
Theory
concept
Cell
All organisms are composed of cells, and new cells only
come from preexisting cells.
Homeostasis
The internal environment of an organism stays relatively
constant, within a range that is protective of life.
Gene
Organisms contain coded information that dictates their
form, function, and behavior.
Ecosystem
Organisms are members of populations, which interact
with each other and with the physical environment
within a particular locale.
Evolution
A change in the frequency of traits that affect
reproductive success in a population or species across
generations.
Visual aid
VIDEO: Animated Science. Episode 1. The Scientific Method
https://www.youtube.com/watch?v=tUP8rFWzVt4
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