Enhancing Thinking Skills in Science Context

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Enhancing Thinking Skills in Science Context

• Lesson 2
• Causal Inference Mills Methods of causal
  reasoning

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Effects
Causes
Inductive reasoning
Causal relationships among events
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Form 5 groups
Study and discuss the given cases
Group presentation
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Activity 1a

• Disease X was recorded long time ago. People with
  disease X would have shaking chills at regular
  time intervals (usually at mid-day between 11
  a.m. to 12 noon), followed by high fever lasting
  for 2 to 6 hours. The patients may also have
  symptoms like headaches, vomiting, delirium,
  anxiety and restlessness.?
• It was also discovered that the blood of the
  infected patients contained a micro-organism that
  was a new species of parasite at that time.

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Activity 1a

• Some doctors also observed that people sleeping
  outdoors were more susceptible to get the disease
  than those sleeping indoors
• ?
• people sleeping near a camp fire were less
  susceptible to get the disease.

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Activity 1a

• A doctor (Dr. R) made a lot of efforts in the
  research of disease X. He observed that Disease X
  was widely spread in the following areas in 1895

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Activity 1a
Place Natural Environment
A Near a river
B Inside a forest
C Near the marshes
D Paddy fields
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Activity 1a

• Dr. R also observed that there were a lot of
  mosquitoes in places A, B, C and D. He suggested
  that mosquitoes might be responsible for the
  transmission of the micro-organisms that caused
  Disease X.

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Task 1a

• 1. Use flow charts / comparison tables /
  diagrams to illustrate how Dr. R arrived at his
  proposition that mosquitoes might be responsible
  for the transmission of the micro-organisms
  that cause disease X.

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Task 1a

• 2. Use simple diagrams to show the logic of
  the causal relationship in case 1(a).

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Activity 1b

• In an uneventful afternoon, four students of
  school A suffered from severe diarrhea. All of
  them went to the hospital and the doctor
  naturally suspected that the symptom might be
  related to the food eaten by the students during
  lunch.

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Activity 1b

• The doctor asked the students what they ate for
  lunch and their answers were as follows

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Student Food items
1 pizza, orange juice, cookie, vegetable salad
2 hot dog, French fries, vegetable salad, iced tea
3 pizza, vegetable salad, coca cola, cheese cake
4 hamburger, orange juice, vegetable salad, cheese cake
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Task 1b

• 1.Use a table / diagram to show the logic of the
  possible cause of diarrhea among the students.
• 2.Do you know the name of this method of
  establishing causal relationship?
• 3.What is the precaution of applying the method
  (in (2)) in causal reasoning?

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Task 1b
Case/event Circumstance Effect
1 B,C, D, A X
2 E, F, A, G X
3 B, A, H, I X
4 J, C, A, I X
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Task 1b

• Mills Method of Agreement (???)

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Task 1b

• You may get the answer vegetable salad from the
  Method of Agreement. But the pathology tests
  showed that there were no bacteria causing
  diarrhea found in the vegetable salad. The actual
  cause why these four students suffered from
  diarrhea was that the forks they used to eat the
  vegetable salad were contaminated with bacteria.
  ?
• People will be blinded by apparent causal
  relationship but in fact there are real reasons
  other than that of observed. For instance, in the
  malaria case above people believed that the cause
  of malaria was marsh but the true reasons are
  that the parasites that cause malaria can be
  carried by mosquitoes that breed in water.

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Activity 2

• Micheal Faradays
• Electro-magnetic
• Induction Experiment

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Activity 2
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Activity 2

• 1. Assemble the above experimental set-up.
• 2. Place a bar magnet into the copper coil (no
  movement of the magnet) and observe the reading
  of the ammeter.
• 3. Place a bar magnet into the copper coil and
  move the bar magnet forward and backward. Observe
  the reading of the ammeter.
• 4. Repeat steps (3) and (4) by replacing the bar
  magnet with an iron bar.

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Task 2

• 1. Design a table to record the results of the
  above experiment.
• 2. Suggest the cause of the change (if any) in
  Faradays Experiment.
• 3. Use a comparison table / diagram to show the
  logic of the discovery by Faraday.
• 4. Do you know the name of the method (in (3)) of
  establishing the causal relationship?
• 5. What is the precaution of applying the method
  (in (4)) in causal reasoning?

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Task 2

• 1. Design a table to record the results of the
  above experiment.
• Answer

Movement of magnet Movement of the pointer of ammeter
Yes Yes
No No
Movement of iron Movement of the pointer of ammeter
Yes No
No No
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Task 2

• 2. Suggest the cause of change (if any) in
  Faradays Experiment.
• Answer
• Its the movement of the magnet that causes the
  pointer of the ammeter moves.?
• Conclusion change of magnetic field causes
  generation of electricity.
• ?

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Task 2

• 3. Use a comparison table / diagram to show the
  logic of the discovery by Faraday.
• Answer

Case/event Circumstance Effect
1 A, B, C X
2 - B, C X
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Task 2

• 4. Do you know the name of the method (in(3)) of
  
• establishing the casual relationship?
• Answer
• Mills Method of Difference (???)
• Remarks
• Mills Method of Difference includes Experimental
  and Control groups.

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Task 2

• 5. What is the precaution of applying the method
  (in(4) in the causal reasoning?
• Answer
• If there are more than one variable in the
  experimental design, the results obtained are not
  conclusive.

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Activity 3

• Discovery of a strange disease by Dr. Sun
  Simiao(???)

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Activity 3

• Dr Sun Simiao(???) (AD 581-682) was a very famous
  doctor in Tang Dynasty. There were several rich
  people living in the capital of China, Changon.
• ?
• All of them got a strange disease at the same
  time.
• ?
• Their symptoms included leg edema, muscle pain,
  fatigue and tiredness.
• ?
• All the famous doctors could not treat the
  diseases.
• ?
• Dr. Sun was invited to treat one of the patients.
  He went to the kitchen of one of the rich
  patients. The cook told him that his master did
  not like to eat too much meat and fish but he
  liked to eat polished rice (white rice which had
  been polished several times). Dr. Sun also paid
  visits to several rich patients who suffered from
  the same diseases. He found that these patients
  had the same habit of eating polished rice.

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Activity 3

• 1. Use a table / diagram to show the logic of the
  discovery of the
• cause of the disease.
• Answer

Case Conditions Conditions Conditions Symptom
Case w x Y (ate polished rice) Leg edema, muscle pain, fatigue and tiredness
Patient A (rich) (ve gp) Yes No Yes Yes
Patient B (rich) (ve gp) No No Yes Yes
C (poor) (-ve gp) Yes No No No
D (poor) (-ve gp) No Yes No No
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Task 3

• 2. Do you know the name of the method (in (1)) of
  establishing the causal relationship?
• Answer
• Mills Joint Method of Agreement and Difference
• (???????)

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Task 3

• 3. What is the precaution of applying the method
  (in (2)) in causal reasoning?
• Answer
• We should consider and compare as many conditions
  and symptoms as possible among the ve and ve
  groups in order to minimise the chance factor.

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Activity 4

• The Discovery of Radium by Marie Curie.

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Activity 4

• In Marie Curies time a radioactive substance,
  uranium was discovered. When uranium compound was
  placed onto a photographic plate covered with
  black paper, it produced an impression analogous
  to that which light would make on that plate. The
  impression is due to uranium rays that traverse
  the paper. These same rays are like X-rays, which
  can discharge an electroscope by making the air
  surrounds it behaves like a conductor.

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Activity 4

• One day when Marie Curie and his husband were
  doing research on some samples containing
  uranium, they discovered that the radioactivity
  measured was far greater than that of uranium.
  They began to suspect that the sample contained
  other radioactive active substances. Then they
  carried out numerous experiments to search for
  the unknown radioactive substance. Finally, after
  45 months hard work the couple isolated a very
  minute quantity of black power, radium chloride
  in 1902.

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Task 4

• 1.Show the logic (method) in the cause of the
  discovery of radium by Marie Curie.
• 2. Do you know the name of the method (in (1)) of
  establishing causal relationship?
• 3. What is the precaution of applying the method
  (in (2)) in causal reasoning?

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Task 4

• 1. Show the logic (method) in the cause of the
  discovery of radium by Marie Curie.
• Answer
• Symbolically, the Method of residues can be
  represented as
• A B C occur together with x y z
• B is known to be the cause of y
• C is known to be the cause of z
• Therefore A is the cause of x
• e.g.
• 1. Let A be Uranium and a be the radioactivity
  measured due to the effect of A
• 2. Let B be the unknown radioactive substance and
  b be the radioactivity measured due to the
  effect of B.
• 3. Since the radioactivity measured was higher
  than expected (a bgta), then the source of the
  radioactivity must come from radioactive
  substance (s) other than A.

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Task 4

• 2. Do you know the name of the method (in (1)) of
  establishing the causal relationship?
• Answer
• The induction method is called Method of
  Residues.

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Task 4

• 3. What is the precaution of applying the method
  (in (2)) in causal reasoning?
• Answer
• Only when it is clear that certain part of the
  phenomenon or observation is due to some
  recognized reason/factors, can the factor/reason
  that can account for the remaining part of the
  observation/phenomenon be confirmed.?
• 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

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Activity 5

• Air pollution increases hospital admissions for
  patients with chronic obstructive pulmonary
  disease in Hong Kong

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Activity 5

• In Hong Kong, Chronic Obstructive Pulmonary
  Disease (COPD) was the 5th leading cause of
  death, and accounted for at least 4 of all
  public hospital acute admissions in 2003. The
  prevalence of COPD among elderly Chinese (age 70
  years) living in Hong Kong is estimated to be 9.
  Previous studies have shown that pulmonary
  function and quality of life among patients with
  COPD were adversely affected by frequent
  exacerbations.

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Activity 5

• A study has just been published in the journal
  THORAX was carried out by the Department of
  Medicine and Therapeutics and the Department of
  Community and Family Medicine, the Chinese
  University of Hong Kong. This study assessed the
  relationship between the levels of ambient air
  pollutants and the hospitalisation rate due to
  COPD in Hong Kong.

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Activity 5

• Data of daily emergency hospital admissions to 15
  major hospitals in Hong Kong for COPD and indices
  of air pollutants (sulphur dioxide SO2,
  nitrogen dioxides NO2, ozone O3, particulates
  with an aerodynamic diameter of less than 10µm
  PM10 and 2.5µm PM2.5) and meteorological
  variables from January 2000 to December 2004 were
  obtained from several government departments.

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Activity 5

• Significant associations were found between
  hospital admissions for COPD with all 5 air
  pollutants. For every 10µg/m3 increase in SO2,
  NO2, O3, PM10 and PM2.5, there was 0.7, 2.6,
  3.4, 2.4 and 3.1 increases in the rates of
  COPD hospitalisations respectively. O3 had the
  strongest effect on COPD hospitalizations. The
  effect of SO2, NO2, and O3 had a stronger effect
  on COPD admissions in the cold season (December
  to March) than during the warm season.

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Activity 5

• Adverse effects of ambient concentrations of air
  pollutants on hospitalisation rates for COPD are
  evident, especially during the winter season in
  Hong Kong. Measures to improve air quality are
  urgently needed.
• (Press Release of CUHK 6 March 2007)

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Task 5

• 1. Use one or two sentences to describe the
  findings of the Chinese University of Hong Kong?
• 2. Please use a table/diagram to represent the
  logic in establishing the causal relationship. Do
  you know the name of the method (in (2)) of
  establishing such causal relationship?
• 3. What is the precaution of applying the method
  (in (2)) in causal reasoning?

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Task 5

• 1. Use one or two sentences to describe the
  findings of the Chinese University of Hong Kong?
• Answer
• Air Pollution Increases Hospital Admissions
  for Patients with Chronic Obstructive Pulmonary
  Disease in Hong Kong.

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Task 5

• Evidence There is a direct correlation between
  the degree to which the cause occurred and the
  degree to which the effect occurred.
• Conclusion A and x has a causal relationship. A
  is the cause of x.

Case/event Circumstance Effect
1 A, B, C X
2 A, D, E X
3 A-, F, G X-
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Task 5

• Concomitant Variation

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Task 5

• a) 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.
• b) Many irrelevant factors would increase or
  decrease concomitantly. For instance, both of the
  average rain falls per year and the birth rates
  in Hong Kong have been decreasing. It is not
  likely that the amount of rainfall affects the
  birth rate.
• c) There is a limit to degree of change in
  circumstance and effect
• d) The circumstance must be the only cause for
  the effect

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Make observations
Analyse and interpret the observations
Draw conclusions about the causal relationships
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Method of Difference ???
Method of Agreement ???
Joint method of Agreement and
Difference ???????
Mills methods in Causal reasoning
Method of Concomitant Variation ???
Method of Residues ???
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What are your comments on Mill?s Methods of
causal reasoning?
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Mills methods of causal reasoning

• Discovery or Proof ?
• - cant be used to discover the cause of some
  observed event
• - can only be used to establish the correlation
  between the occurrences of distinct events

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Mills methods of causal reasoning

• Confirmation
• - as tools for confirming
• hypotheses
• - useful if we have already
• proposed several specific hypotheses about
  what may be the cause of an observed event