The document discusses problem statements and their components in scientific experiments. It defines a problem statement as the question being investigated in an experiment. A good problem statement is a single, open-ended question that identifies the independent variable being changed and dependent variable being measured. It provides examples of good and poor problem statements and teaches how to identify the independent and dependent variables within a given problem statement.

1. 11
Scientific MethodScientific Method
Writing a Purpose StatementWriting a Purpose Statement

2. 22
What is a Problem Statement?What is a Problem Statement?
 The question that you select forThe question that you select for
your investigation – the basis ofyour investigation – the basis of
your experiment.your experiment.
 The research and experimentThe research and experiment
you will be conducting centeryou will be conducting center
around finding an answer to thearound finding an answer to the
question or problem statement.question or problem statement.

3. 55
AA Good Problem StatementGood Problem Statement
(or Purpose)(or Purpose)
 The problem statement only needs to beThe problem statement only needs to be
one sentence longone sentence long..
 The problem statement isThe problem statement is alwaysalways in thein the
form of aform of a questionquestion..
 Should beShould be open-endedopen-ended (not answered by(not answered by
yes or no)yes or no)
 A problem statementA problem statement includes what isincludes what is
changedchanged (independent variable) and(independent variable) and
what iswhat is measuredmeasured (dependent variable).(dependent variable).

4. 66
A Good Problem StatementA Good Problem Statement
How does light affect the reproductionHow does light affect the reproduction
of bread mold on white bread?of bread mold on white bread?
Note the question is about:Note the question is about:
 one life processone life process
 one type of moldone type of mold
 one type of breadone type of bread
 one factor that affects it growthone factor that affects it growth
(reproduction)
(bread mold)(bread mold)
(white bread)(white bread)
(light)(light)

5. 77
A Poor Problem StatementA Poor Problem Statement
How does light affect molds?How does light affect molds?
Note the question would have to test:Note the question would have to test:
 all the life processes of moldall the life processes of mold
 all types of moldall types of mold
 all types of growth mediumsall types of growth mediums
 one factor that affects its growth (light)one factor that affects its growth (light)

6. 88
Choose a problem that can beChoose a problem that can be
solved experimentallysolved experimentally
Look at each question below and evaluate. Is it an example
of a good or poor problem statement? Explain why.
What is mold?
 Poor problem statement because it can be answered by
finding the definition of the word mold in the dictionary.
Will a green plant stay green if grown in the dark?
 Poor problem statement because it can be answered by
a yes or no.
How does temperature affect the growth rate of bread mold
on white bread?
 Good problem statement because it can be answered
by experimentation.

7. 99
Independent VariableIndependent Variable
 The experimenter changes only one
variable in an experiment.
 This is important so we can see the
effect of changing that variable.
 The variable that is changed is called
the independent variable (test).

8. 1010
Dependent VariableDependent Variable
 The experimenter measures or observes the change
caused by the independent variable.
 The variable that is measured or observed is referred to as
the dependent variable (outcome).
 As a result of changing the IV
 The measure should include the units of measurement.
(i.e., count, percentage, length, width, weight, voltage,
velocity, energy, time)
 If the experimenter observes the change, then the
observed variable should be obvious. (i.e.,
color change, lights on in one trial, then lights off in another
trial)

9. 1111
Good Problem StatementsGood Problem Statements
Practice identifyingPractice identifying
independent and dependent variables.independent and dependent variables.
Question Independent Variable
(What is changed?)
Dependent Variable
(What is measured?)
Water faucetWater faucet
openingopening
(closed, half open,(closed, half open,
fully open)fully open)
Amount of waterAmount of water
flowing measuredflowing measured
in liters per minutein liters per minute
Amount of fertilizerAmount of fertilizer
measured inmeasured in
milliliters (mL)milliliters (mL)
Growth of the plantGrowth of the plant
measured bymeasured by
increase in massincrease in mass
measured in gramsmeasured in grams
How much water
flows through a
faucet at different
openings (closed,
half open, fully
open)?
How does the
amount of fertilizer
affect the growth of
a tomato plant (as
measured by an
increase in mass)?

10. 1212
Question Independent Variable
(What is changed?)
Dependent Variable
(What is measured?)
The group receivingThe group receiving
the survey:the survey:
teenagers orteenagers or
parentsparents
The amount of timeThe amount of time
each person watcheseach person watches
television per daytelevision per day
measured in hoursmeasured in hours
Voltage of theVoltage of the
electricityelectricity
measured in voltsmeasured in volts
Speed of rotationSpeed of rotation
measured inmeasured in
revolutions perrevolutions per
minute (RPMs)minute (RPMs)
Good Problem StatementsGood Problem Statements
Practice identifyingPractice identifying
independent and dependent variables.independent and dependent variables.
Who watches
television the
most in a day:
teenagers or their
parents?
What effect does
increasing the
voltage have on
the rotation speed
of an electric
motor?

11. Identifying purpose statements
& variables

12. 1. Which problem statement is
worded the best?
1. 2. 3. 4.
0% 0%0%0%
1. Does boiling an egg change its mass?
2. How does boiling an egg affect its mass?
3. What effect does boiling have on an egg?
4. Is mass changed when you boil an egg?

13. 2. What would be the independent variable
in this problem statement:
“How does the position in which a seed is
planted affect how quickly it sprouts?”
1. 2. 3. 4.
0% 0%0%0%
1. The amount of time it takes to sprout
2. The number of seeds planted
3. The position in which seeds are planted
4. The height of the sprouted plant

14. 3. What would be the dependent variable in
this problem statement:
“How does the position in which a seed is
planted affect how quickly it sprouts?”
1. 2. 3. 4.
0% 0%0%0%
1. The amount of time it takes to sprout
2. The number of seeds planted
3. The position in which seeds are planted
4. The height of the sprouted plant

15. 4. True or False: A good problem
statement should always be worded
so it can be answered by yes or no.
1. 2.
0%0%
1. True
2. False

16. 5. True or False: A good problem
statement should always be worded as
a question.
1. 2.
0%0%
1. True
2. False

17. 6. What would be the dependent variable in
this problem statement:
“Which food (apple, potato, or tomato) will
produce the highest amount of energy
measured in voltage?”
1. 2.
0%0%
1. The amount of energy
2. The type of food (apple, potato, or tomato)

18. 7. What would be the independent variable
in this problem statement:
“Which surface (grass, sidewalk, road) will
the RC car have the fastest speed over a
distance of 10 meters?”
1. 2.
0%0%
1. Speed of RC car over 10 meters
2. The type of surface (grass, sidewalk, road)

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Now, pick 1 bad problem statement and re-write
it to make it better. Use the following
templates or your own:
 What is the effect of (a) on (b)?
 How does (a) affect (b)?
 In what way does (b) depend on (a)?
 Which (a) will (b)?
(a) - is the independent variable
(b) - is the dependent variable