JSSS
Teacher material
Carrying out an investigation
Problem statement
Turn the topic into a problem statement. The problem statement is a sentence or question that
identifies the independent and dependent variable.
Remember not to make sweeping statements. If you only have one species of plant, you can only
come to a conclusion about that species of plant. Your results may not hold true for other species
of plant.
If we consider the investigation title
“Investigate how watering plants affects the way they grow”
Possible problem statements (these are not the only possibilities):

How does the amount of water (independent variable) affect the height (dependant
variable) of plants?

How does the amount of water (independent variable) affect the numbers of leaves
(dependant variable) a plant produces?

How does the number of leaves (independent variable) affect the amount of water
(dependant variable) taken up by plants?

How does the time of day (independent variable) that plants are watered at affect their
height (dependant variable)?

How does the amount of light a plant is exposed to (independent variable) affect the
uptake of water (dependent variable)?
It is important that each of the variables can be measured
Hypothesis/ prediction
Once you know what problem statement you wish to solve, you should make an educated guess
about how the experiment will turn out. The hypothesis is a statement about what you think the
answer to the problem statement will be. This may be based on prior knowledge or just an
educated guess, or as a result of literature research. The hypothesis should connect the dependent
and independent variable, the reason for the connection should also be there.
E.g. If the amount of water given to a plant is increased, then the height of the plant will
increase because more water will be available for photosynthesis.
-1-
JSSS
Teacher material
Planning
Once the problem statement has been made, all the other things that might affect the outcome of
the investigation can be identified so as to ensure a fair test. In all of the problem statements
above, both the independent and dependent variable can be measured.
The plan should include information about what you are going to measure, the number of times
each of the levels of the independent variable is to be tested and a list of all the constants that are
to be kept the same.
A simple chart can be used to outline your plan
What you are going to change
(independent variable)
Level of change
Number of times you will repeat the
trial at this level
What you are going to measure that
will change as a result of changing the
independent
variable
(dependant
variable)
Constants
If we use the example given above for the hypothesis, this chart might look like this:
What you are going to The amount of water that we give a selection of plants.
change
Level of change
20cm3/day 40cm3/day
60cm3/day 80cm3/day 100cm3/day
Number of times you will 5
5
5
5
5
repeat the trial at this level
What you are going to The height of the plants
measure that will change as a
result of changing the
independent variable
Constants
Light, type of plant, initial height, humidity, temperature, type of
water, temperature of water, placement of water, number of
leaves, type of pot.
-2-
JSSS
Teacher material
Analysis
It is important to tabulate any results clearly so that you can identify trends and patterns, and
analyse the data. You should decide how you will present your results.
A sample table of results for the investigation outlined above might be:
Water
1
2
3
4
5
added
Average
height
cm3/day
increase/cm
20
3.2
3.3
3.7
3.6
3.5
3.46
40
4
4.3
4.1
4.4
4.2
4.23
60
5.6
5.7
5.5
5.3
5.2
5.46
80
5.4
5.5
5.6
5.5
5.3
5.46
100
5.3
5.5
5.6
5.5
5.2
5.42
This could then be represented graphically
cm3/day
-3-
JSSS
Teacher material
Comments

restate the hypothesis

use the analysis to explain if the hypothesis was supported by the data

if the hypothesis was not supported by the experiment, explain what you think happened
if appropriate, state an alternative hypothesis

discuss other factors that may have affected your results (e.g. other variables that you
could not or did not control)

discuss errors you made in the investigation

discuss questions such as:

what is the importance of this experiment?

what impact could these results have?

how this study could be refined based on what I have learned?

what if any implications could this have in the real world?
-4-