VARIABLES
Independent vs.
Dependent
9/9 P. 12 VARIABLES & HYPOTHESES
IQ: Jane did an investigation to see the
effect of temperature on the growth of mold
on a slice of bread. She left one slice in the
fridge and another on her kitchen counter.
What is independent var. and the
dependent variable in this experiment?
VARIABLE
Variable- Something that is
changed in an experiment.
 In scientific experiments there
are two variables- One that you
control and one that is the result.
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INDEPENDENT VARIABLE- “THE CAUSE”
The one thing that is
changed by the experimenter
 In a graph it is on the xaxis(along the bottom)
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Ex. The amount of explosive
chemicals inside a firecracker.
DEPENDENT VARIABLE
The result of the experiment
 What is measured
 This “depends” on what you
changed- the IV.
 On a graph, it is on the yaxis(along the vertical side)
 Example: the loudness of a
firecracker (d.v.) depends on
the amount of explosive
chemicals used (i.v).

GRAPHING VARIABLES

Direct Relationship
Inverse relationship
THE IV CAUSES THE DV TO CHANGE
1. The temp. of the water was
measured at different depths of the
lake.
 Two things were changed in this
statement.
 The first was the depths and the
second was the temperature .
 Plug these into the bolded
statement:
 The depth causes the temp to
change.
 IV: depth
 DV: temp
2. The amount of time you study will
make a positive difference on your next
test score.
 Two things are changed: 1. Time spent
studying 2. Score on next test.
 The ____________causes _________ to
change.
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IV: ____________ DV: _____________
CONTROL VARIABLE
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A Control variable is anything else that could
influence the dep. var.
Control variables must be carefully
monitored and kept equal/same in the
experiment or they could mess up the results
by making your results false or unreliable.
For example, when testing to see if a plant
that is given fertilizer grows taller than one
without:
What is the IV? :_________What is the
DV?:_________
What other variables could also affect the
growth of the plants? ___________________.
These are the control variables and should be
kept the same for both plants.

Control setup/group- Part of the experiment that
does NOT get any special treatment, IV is not
changed or introduced.
DEVELOPING HYPOTHESES
Problem has been stated
Question
Research
(Using your five senses and prior knowledge)
A Hypothesis is formulated
WHAT IS A HYPOTHESIS
A hypothesis is an inference (based on
observations and prior knowledge) about
what will happen in an experiment.
 The hypothesis should tell what you will
do or how the IV will change, predict
what the answer to your question will be
or how the DV will be affected, and give
reasons why.
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FORMAT FOR WRITING A HYPOTHESIS

Most of the time a hypothesis is written like this: "If
_____[I do this] _____, then _____[this]_____ will
happen, because ________ [mention your research or
prior knowledge]" (Fill in the blanks with the
appropriate information from your own experiment.)
If
I press harder on the gas
pedal, then I will get a ticket
because I will go past the
speed limit.
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Your hypothesis should be something that you can
actually test, what's called a testable hypothesis. In
other words, you need to be able to measure both "what
you do" and "what will happen."
MORE EXAMPLES OF HYPOTHESES
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"If I open the faucet [faucet opening size is the
independent variable], then it will increase the flow of
water [flow of water is the dependent variable],
because more water can come out at a time.
"Raising the temperature of a cup of water [temp. is
the IV) will increase the amount of sugar that
dissolves [amt. of sugar is the DV], because the
molecules will move faster."
"If a plant receives fertilizer [having fertilizer is the
independent variable], then it will grow to be bigger
than a plant that does not receive fertilizer [plant size
is the dependent variable], because fertilizer adds
more nutrients to the soil."
P.
12
OQ: Determine IV and DV, and create a hypothesis
for the following question:
How will my overall class grade be affected by my
score on Friday’s test?
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Practice: In the scenario below, identify the following
components of an experiment. Underline and number them
on the paragraph.
 Independent variable
 Dependent variable
 Hypothesis
 Control setup
 Control variables/Constants
Scenario
Jack wanted to test which brand of car wax was most
effective. He tested four brands (A-D) of wax. He proposed
that drops of water would spread the most on the wax that
worked the best as the waxed surface would be more slippery.
He cleaned the hood of his car and removed the old wax. He
measured five equal sections on the hood of the car. Each of
the waxes was used to cover a section, and one section was
left un-waxed. An equal amount of wax, the same type of rag,
and equal buffing were used. Ten drops of water were placed
on each square, and the diameter of each drop was measured
(cm).
Practice: Find the error/s in the following experimentJoAnna read that certain perfume esters would agitate
bees. Because perfume formulas are secret, she decided
to determine whether the unknown Ester X was present
in four different perfumes by observing the bees’
behavior. She placed a saucer containing 10 mL of the
first perfume 3 m from the hive. She recorded the time
required for the bees to emerge and made observations
on their behavior. After 30-minute recovery periods,
she tested the second, third, and fourth perfumes in 10
mL quantities. All experiments were conducted on the
same day.
9/10 GUMMY BEAR LAB
IQ: A student is doing an investigation for the
following question:
What is the effect of rainy weather on school
attendance?
IV:_____, DV:________
Hypothesis: ________________
Type of relationship between variables:________
(direct or inverse)
GUMMY BEAR LAB
You will be seeing the effects of leaving a gummy
bear in water overnight.
 You will be working on your own or with a
partner.
 Make sure to label your cup before leaving today.
 What are some things/qualities you could observe
in a gummy bear to see if it gets affected by
water overnight?
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ACC
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Design a controlled experiment (need a control
setup) with at least 2 experimental setups where a
gummy bear is left in a liquid overnight.
Decide on your independent (what will you change
or expose the gummy bear to) and dependent
variables (which characteristic/s will you observe to
see if they get affected), create a question and start
your lab report.
You may work individually or with a partner.
Materials available: Rubbing alcohol, hydrogen
peroxide, water, lemon juice, vinegar, cup (50 mL),
gummy bears, ruler, triple beam balance, graduated
cylinders (50 mL)
You should be done through your data table (show
me) to be able to start the lab.
P.
15 GUMMY BEAR LAB
 Question:
How is the length and ________ of
a gummy bear affected if it is soaked in water
overnight?
 Research: (Record observations and prior
knowledge)
 Hypothesis: If ___________________________,
then its length will ______________ and its
____________ (mass, smell, color, texture) will
_______________, because __________________
Procedures:
1. Measure and record length of gummy bear.
2. Observe/measure ___________ of gummy bear
and record.
3. Fill cup with water about 3/4 full.
4. ____________________________________________
____________________________________________
5. ____________________________________________
____________________________________________
DATA TABLE
Day
Length (cm)
______________
P.
14
OQ: Give an example of a control setup for today’s
lab.
GET A PAPER TOWEL AND TAKE YOUR GUMMY
BEAR OUT OF THE WATER AS YOU COME IN. DO
FINAL OBSERVATIONS AND RECORD!
9/11 P.16 GUMMY BEAR LAB CONT’D
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IQ: Which type of graph would be best suited for
the data you collect from the gummy bear lab?
After finishing your test:
 Fill in and complete data table
On p. 17
 Create a graph or graphs for your data. Use the
sheet on p. 3 to decide which type of graph to
draw.
 Conclusion:
 Repeat your results with more
details/comparisons.
 Was your hypothesis supported or not?
 What inferences can you make from your results
or what did you learn from your experiment?
 What are some questions you have or how would
you like to do this experiment differently in the
future?
OQ: List at least 3 control variables in the gummy
bear lab.
CREATE A HYPOTHESIS FOR EACH OF THE
FOLLOWING QUESTIONS:
Which textbook is heavier, Math or
Geography?
 Which city is more populated, Seattle or
Las Vegas?
 OQ: Create a question given the
following 2 variables:
IV: Time spent exercising.
DV: Heart health
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