Scientists use many methods in their
research, such as descriptive
investigation, simple mathematical and
engineering modeling and design, and
controlled experiments. Students should
learn a variety of methods to solve
problems and make sense of the world.
(6.2, 7.2, 8.2) Scientific processes. The student uses
scientific inquiry methods during field and laboratory
investigations. The student is expected to
(A)plan and implement investigative procedures
including asking questions, formulating testable
hypotheses, and selecting and using equipment and
(B) collect data by observing and measuring;
(C) organize, analyze, evaluate, make inferences, and
predict trends from direct and indirect evidence
(D) communicate valid conclusions; and
(E) construct graphs, tables, maps, and charts using
tools [including computers] to organize, examine, and
Experimental Design using
When scientists begin an
experiment they use the
steps of the Scientific
Method. You will be asked
to understand many of
these steps on the TAKS
The Problem (in the form of a
question) that the scientists will try
to answer, must be logical and based
on data or observations.
A prediction called a Hypothesis is
next. It must be a testable
statement that you could gather
data to prove. (You can’t measure
which is the “prettiest”,
“strongest”, or “best”.)
You must control an experiment. You can test
only one variable at a time. (How does the
amount of water effect plant growth? Keep
the light, containers, soil and plants the
Controls: Light, type of plant,
amount of soil, pot, temperature.
500ml 400ml 300ml
A Control Group is the set-up that
isn’t changed. (One plant gets the
normal amount of water!). Which
group above is the control group?
The independent variable is the thing you
change (amount of water). The dependent
variable is the result of the change you
made(height of plant in cm.).
variable: Amount of
water given in mm.
Plant growth in cm.
When reporting the
results, the Independent
Variable is graphed on
the X-axis. The
Dependent variable is on
Growth in mm
DRY MIX = Dependent
Responding Variable on
Amount of Water
Independent Variable on
The Conclusion must be supported by the data
and results you gather. To be valid, each
experiment needs a large sample size (grow
2000 plants in each experiment) and must be
repeated many times in order to prove the
Hypothesis (grow 2000 plants 100 times). If
you are collecting samples, in an experiment, do
it randomly. Don’t take them all from one place.
Check for understanding
Check for understanding by answering
the following questions.
Remember that you are using the scientific
method in investigations.
Which of these is a hypothesis that can be
tested through experimentation?
F Bacterial growth increases as temperature
G A fish’s ability to taste food is affected by The pH
of aquarium water.
H Tadpoles’ fear of large insects increases as the
J The number of times a dog wags its tail indicates
how happy the dog is.
The correct answer is A. Bacterial
growth can be measured. Dog
happiness, fish fear, and tadpole
taste cannot be measured
The table shows times required
for water to evaporate from
identical containers. Which of
these is the best question to ask
before developing a reasonable
hypothesis to explain the data?
A Does a lower temperature slow
the rate of evaporation?
B What is the boiling point of
the water after both samples are
C Why does water exist as a
solid at -15°C and as a liquid at
D How does the rate of
evaporation change when a
different container is used?
The correct answer is A. The
table shows data taken to
investigate temperature and
the evaporation of water.