Suggested Learning and Teaching Activities
Lesson 2 Causal Inference-Mill’s Method in Causal Reasoning
Level of Students: S.1-S.2
Suggested Lesson Time: 90 min.
Learning Objectives:
Students will:
gain an understanding of Mill’s Method in causal reasoning
be able to use Mill’s Method to analyse and interpret observations for the purpose of drawing
conclusions about the causal relationships they exhibit
be able to understand the limitations of Mill’s Method in causal reasoning
Materials and Apparatus for each group:
1 ammeter, 1 copper coil, 1 bar magnet, 1 iron bar, connecting wires
Prior knowledge of students:
Students should have the basic knowledge of scientific investigation learnt in S.1. The teacher can ask
students a few simple questions on causal reasoning to understand how much they know on the topic.
Suggested Learning
and Teaching
Activities:
Lesson 2
Causal
Inference-Mill’s
Method in causal
reasoning
Time
allocation
Remarks
90 min.
The students are divided into groups of 4-5 members. The
team-mates are required to discuss the cases together and
prepare a presentation. The teacher then discusses the findings
with the students and comments on the use of Mill’s Method in
causal reasoning.
Activity 1a & 1b
(Method of
Agreement)
20 min
The focus of Activity 1a and 1b is to let students know the logic
of using Method of Agreement (Mill’s method) in causal
reasoning and its limitation:
People will be blinded by apparent causal relationship but
in fact there are real reasons other than that of observed.
Cannot observe all possible cases
Activity 2
(Method of Difference)
20 min
The focus of the Michael Faraday’s Experiment is to let students
know the logic of using Method of Difference (Mill’s method)
in causal reasoning and its limitation:
If there are more than one variable in the experimental
design, the results obtained are not conclusive.
Teacher may ask the following question to relate “fair test” to
Method of Difference:
“We usually use “fair test” in scientific investigation. Does the
“fair test” idea match with Mill’s Method of Difference?”
Suggested answer:
Mill’s Method may include two or several experimental groups
and one control group. In this sense it is similar to fair test
experiments.
Activity 3
(Joint Method of
Agreement and
Difference)
20 min
The focus of Activity 3 is to let students know the logic of using
Joint Method of Agreement and Difference in causal reasoning
and its limitation:
Should observe more cases to minimise the chance factor,
otherwise cannot avoid co-incidence or unrelated situations
Activity 4
(Method of
Residues)
10
min.
The focus of Activity 4 is to let students know the logic of using Method of
Residues in causal reasoning and its limitation:
Sometimes it is difficult to use the Method of Residue to find the causal
relationship because the remaining factor found is a compound factor. As in
the discovery of radium, Marie Curie first isolated Po (plutonium) and then
found radium which contributed to the major difference in the observed
radioactivity of the uranium sample.
Activity 5
(Method of
Concomitant
Variation)
20
min.
The focus of Activity 5 is to let students know the logic of using Method of
Concomitant Variation in causal reasoning and its limitation:
Two events have correlation but it is not necessary for them to have
causal relationship. For instance, many overweight people would die at
young ages. However, overweight is not a direct cause of early death.
Many irrelevant factors would increase or decrease concomitantly. For
instance, both the average rain falls per year and the birth rates in Hong Kong
have been decreasing. It is unlikely that the amount of rainfall affects the
birth rate.
There is a limit to the degree of change in circumstance and effect.
The circumstance must be the only cause for the effect.