PRE-TEST : Scientific Method
Name:_________________________________________
ONLY answer questions that you believe you
know the correct response to. Don’t guess or
make things up.
1. In a valid experiment there is only one:
A.
B.
C.
D.
independent variable
measured variable
controlled variable
I am not sure of the answer to this question
2. Repeating an experiment is done to:
A.
B.
C.
D.
E.
Check the reliability of the data
Increase the accuracy of the data
Enable a variety of people to make observations of the results
Ensure that all possible causes for result have been tested
I am not sure of the answer to this question
3. When the independent variable provides continuous data the data is best displayed in a:
A.
B.
C.
D.
Pie chart
Line graph
Column/bar chart
I am not sure of the answer to this question
4. Data that is obtained by making subjective assessments is referred to as:
A.
B.
C.
D.
Quantitative data
Qualitative data
Invalid data
I am not sure of the answer to this question
5. In a valid experiment:
A.
B.
C.
D.
All variables must be kept the same between a treatment group and the control group
There must only be one treatment group and one control group
Only one variable must differ between a treatment group and the control group
I am not sure of the answer to this question
2. Arushi is a keen gardener who wants to
maximize her yield of vegetables. She wants to find
out if adding different volumes of her favourite
fertilizer will have an impact on the growth of her
potted cabbage plants.
Arushi formed a hypothesis and went about testing it.
She set up 5 pots, each containing 10 small
cabbage plants. Each plant was 4-5cm tall, each
pot had the same amount of potting mix in it.
On the day after the cabbages were planted, Arushi added different amounts of liquid fertilizer to each pot.
From then on she watered the plants with the same amount of water each day. She observed the plants
again after allowing them to grow for 10 days. Her results are shown below.
Effect of different volumes of fertilizer on the leaf colour and height of cabbage plants after 10 days
Pot
Volume of liquid fertilizer
added(mL)
0
5
10
15
20
1
2
3
4
5
Observations after 10 days
Colour of leaves
Average height(cm)
Pale green
8
Green
8
Green
15
Green
16
Yellow
8
a) Suggest a hypothesis that Arushi may have been testing.
A variety of answers are acceptable but must be phrased as a statement not a question and must
link IV and DV. For example
That the higher to volume of fertilizer applied to cabbage plants the taller they will grow
b) What is the independent variable in the experiment? the volume of fertilizer applied to the
cabbage plants
c) What is the dependent variable in the experiment? the height of the cabbage plants
d) What are the controlled variables in her experiment?






same type of fertilizer used in each set up
same type of plant used (all cabbage plants)
same number of cabbage plants in each pot
All plants left to grow for the same amount of time(10 days)
cabbage plant initially were of similar size
same volume and type of potting mix used in each pot
encourage students to list them in order of most significant controlled variable to least
significant and to use the term SAME(or a substitute term) in each point
e) Leaf colour data is qualitative/quantitative (strike out the term that doesn’t apply)
f)
Height data is qualitative/quantitative(strike out the term that doesn’t apply)
g) (i) What type of graph would be used to depict the data for average height vs volume of liquid
fertilizer? Line graph
(ii) In the graph which variable would be placed on the horizontal axis? Volume of fertilizer
h) What is the advantage of having 10 plants in each pot?
This increases the reliability of the data and enables an average height to be calculated which
reduces the impact of any single anomalous result
i)
What conclusion can you draw from her results
In can be concluded that increasing the volume of fertilizer did not always increase the height of cabbage
plants and so the hypothesis is not supported by this data.
(an increase in volume of fertilizer from 0 to 5 didn’t increase the average height of the cabbage plants
and nor did an increase from 15ml to 20ml. These results would lead to a modified hypothesis being
formed and tested….what might that be?)
2. Four pairs of students carry out an experiment into the effects of exercise of pulse rate. Their methods
are as follows.
A. May and Charlotte run on the spot for 2 mins and then take each other’s pulse.
B. Samaria takes Joyce’s pulse while Joyce is seated. Joyce then runs on the spot for 2 mins and
Samaria takes her pulse again.
C. Drew runs on the spot for 2 mins and Melanie then takes her pulse
D. Kelly runs on the spot for 2 mins then takes her own pulse. Shona sits and takes his own pulse.
Consider the method use by each pairs of students.
a) Which students are the most likely to be able to make a valid conclusion about the effect of
exercise on pulse rate? Give a reason for your choice
B. Samaria takes Joyce’s pulse while Joyce is seated. Joyce then runs on the spot for 2 mins and
Samaria takes her pulse again.
Of the four experiments, this is the ONLY experiment that is well controlled. There is ONE test
subject and there is a control set up(pulse rate at rest) which acts as basis for comparison with
the treatment group.(pulse rate after exercise) This would enable the students to state that any
difference in pulse rate between rest and exercise was due to the exercise.
------------------------------------------------------------------------------------------------------------------------------NOTE
A. Has two subjects but no control group for either, so nothing to compare the after exercise
pulse rates to.
C. measures pulse rate of one subject after exercise but there is no base line to compare it to
D. Has the resting pulse of one student and the after exercise pulse rate of another, so these
can’t be compared(the person is different)
The control is when
b)
How could their experiment be improved?
Repeat the experiment with Joyce exactly as it has been done several times and average the
results.
Following this you could also have Samaria do this same experiment several times and
average her results.