Transcript Scientific Method - Deer Valley Unified School District

S CIENTIFIC M ETHOD
S TEPS IN THE S CIENTIFIC
M ETHOD

Observation

Hypothesis

Experiment

Data Collection

Conclusion

Retest
O BSERVATIONS

Gathered through
your senses.

A scientist notices
something in the
natural world.

Repeated
observations
over a long
period of time.
O BSERVATIONS

An example of an
observation might be
that young dolphins
and small porpoises
with horrific injuries
continually show up on
the shores of Virginia
and Scottland’s East
coast.
H YPOTHESIS

A suggested solution
to a problem.

Must be testable.

Written as an
“If…then…”
statement.

Predicts an
outcome.
H YPOTHESIS

A hypothesis might be that the
mammals had died through
'blast trauma'. In American
cases, this was supposedly from
exercises by the US Navy, and in
Scotland from air guns used by
oil rig technicians to detect
undersea caverns.
E XPERIMENT

A procedure to test
the hypothesis.

Can be an
experiment, model,
or observation.
The hypothesis was dismissed after
further examination of the mammals'
bodies revealed the injuries - broken ribs,
imploding lungs, damaged livers and
massive internal bleeding - could only
have come from prolonged, focused
attacks.
When tell-tale teeth-marks were
identified, the dolphin - the mammal
classified as one of the world's most
intelligent, sensitive and sociable
creatures - became the official suspect.
Confirmation of the murders came by way
of two shocking films shot by
holidaymakers.
A G OOD E XPERIMENT

Will be repeatable.

Change only one
variable at a time.

Will have a large
sample size.
VARIABLES , C ONTROLS , AND
C ONSTANTS
S CIENTIFIC E XPERIMENTS
F OLLOW R ULES

An experimenter
changes one
factor and
observes or
measures what
happens.
VARIABLES

Variable

Factor in the
experiment
that is being
tested.
I NDEPENDENT VARIABLE

The factor that is
changed by the
experimenter is
known as the
independent
variable.


Its effects are
measured by
changes in the
dependent
variable
It will be graphed
on the X-AXIS
D EPENDENT VARIABLE

The factor that
is measured or
observed is
called the
dependent
variable.

Observed and
measured
during the
experiment

Graphed on the
Y-AXIS
G RAPHING VARIABLES
Metabokic rate (arbitary units)
Metabolic rate of a rat at different temperatures
14
12
10
8
6
4
2
0
0
10
20
30
40
50
Temperature (degree celcus)

The independent variable would be the temperature.

The dependent variable is the metabolic rate.
C ONSTANTS

The
experimenter
makes a special
effort to keep
other factors
constant so that
they will not
effect the
outcome.
Susie want to know how different colors of light effect
the growth of plants. She buys 5 ferns of the same
species, which are all approximately the same age and
height. She places one in white light, one in blue light,
one in green light, one in red light, and one in a closet.
All of the ferns are planted in Miracle Grow and given 20
mL of water a day for two weeks. After the two weeks,
Susie observes the plants and takes measurements.
In this experiment, the species, age, original height, the soil and amount
of water are ALL constants.
C ONTROLS

Establish a “status quo”

How conditions are
under normal
circumstances.

Controls are NOT being
tested.

Controls are used for
COMPARISON
E XAMPLE …

Susie want to know how different colors of light effect the
growth of plants. She buys 5 ferns of the same species,
which are all approximately the same age and height. She
places one in white light, one in blue light, one in green
light, one in red light, and one in a closet. All of the ferns
are planted in Miracle Grow and given 20 mL of water a
day for two weeks. After the two weeks, Susie observes
the plants and takes measurements.
VARIABLES IN THIS
EXPERIMENT …

Variations in the light color are
the independent variables

Growth in the plants are the
dependent variables

Having the same species at the
same age, starting out at the
same height, using the same
soil and amount of water are all
constants.

The plant that was placed in the
closet is the control.
W HY DO SCIENTISTS REPEAT
EXPERIMENTS ?

In order to verify results, experiments must be
RETESTED!

It adds validity to the findings.
VALID E XPERIMENTS

Two groups are
required --- the
control &
experimental
groups

There should be
only one variable
each experiment
D ATA

Results of the
experiment

May be
quantitative
(numbers) or
qualitative
(descriptive)
D ATA

Must be organized

Can be organized
into charts, tables,
or graphs
T RENDS

Negative (inverse)


Positive (direct)


When one increases, the other
decreases
When one increases, the other
increases OR when one
decreases, the other decreases
No relationship

One has NO EFFECT on the
other.
IN
D ATA
C ONCLUSION

The answer to
the hypothesis
based on the
data obtained
from the
experiment
H OW DO SCIENTISTS
COMMUNICATE FINDINGS ?

When scientists want to communicate the results
of their experiment, they use SCIENTIFIC
JOURNALS or other publications!
P URE AND A PPLIED S CIENCE

Pure Science

Answers questions about phenomena
and mechanisms in the natural world.

Why do you do it?

Because we wanted to know!


EX. Studying the dolphin deaths
Applied Science

Application of scientific knowledge to
practical problems.

Why do you do it?

To fight disease, identify criminals,
learn how to store hazardous
wastes…etc.