Chapter 6. Discussion through Development of Teaching Unit
6.2 Teaching experiment of the developed unit
6.2.3 Analysis of teaching experiment from the perspective of ‘causal inquiry’
First of all, the author analyses it from the viewpoint of ‘causal inquiry’. The author would like to show how the beginnings of statistical literacy at the critical/mathematical level (Watson & Callingham, 2003) emerge by giving two examples of explanations, one data-based and the other word-based. The data-based explanation was given in the group presentation in the 3rd lesson. The following statement was made using the portion enclosed in the handwritten boxes in Figure 6-3 by Group A.
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Figure 6-3. The graph used in Group A’s presentation in the 3rd lesson (with handwritten parts by group A; translated by the author)
Group A: … there are other researchers studying the correlation between the global temperature and carbon dioxide. These indicate at a glance a strong correlation between these two. If we examine them carefully, we find that there is indeed a correlation, but the causal relationship is completely the opposite. Instead of the temperature rising after carbon dioxide increased, we found that the temperature increased first, and after a little while, carbon dioxide increased.
…
Group A found Figure 6-3 using the Internet,7 and argued using the graph that CO2 is not the cause of global warming. Regarding this, there are many overlapping parts of the analysis from the viewpoint of emergent hypothesis modelling, but it is hard to imagine that Group A focused on the temporal relationship between CO2 and temperature spontaneously after finding Figure 6-3 on the Internet.
In other words, it is more likely that they had a purpose of finding data showing an increase in CO2 after the temperature rise before they found Figure 6-3. Therefore, it can be said that this explanation using Figure 6-3 by Group A is a causal inquiry based on data.
Next, the word-based explanation emerged in the presentation by Groups B and C in the 6th
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lesson. Both groups were opposed to the hypothesis that CO2 is the cause of global warming, and gave presentations about the results of inquiring into the causes of global warming besides CO2 from which the following passages are quoted:
Group B: … According to the latest research, when oceans become oxidized, the production of dimethyl sulfate declines. … Plankton in the sea produces dimethyl sulfate. It is said that dimethyl sulfate … becomes the source of clouds. … The resulting large amount of clouds blocks sunlight and decreases the Earth’s temperature. … A certain amount of CO2 in the atmosphere dissolves into the oceans, lowering the pH level of oceans, that is, oceans become acidic.
Therefore, the more CO2 levels in the atmosphere increase, the more oxidized the oceans will become. …
Group C: … if the sunlight is pouring over the Earth with its full strength, then clouds reflect back 75%
of it, and the remaining 25% hits the Earth and contributes to the Earth’s temperature. As the other group (Group B) said, the amount of clouds above oceans is decreasing, which means that the reflective power of the clouds is also decreasing. Consequently, the heat of the sun directly hits the Earth. …
The result of the inquiry by these groups is shown as follows in the form of ‘(cause) → (effect)’:
CO2 increase → acidification of the sea → dimethyl sulfate decrease → cloud decrease → amount of sunlight (the influence of the solar energy) increase → temperature rise (global warming). In this scheme, no data from the causal inquiry have been presented, so it can be considered a word-based causal inquiry.
It is contextual thinking that is always raised in causal inquiries based on words. As explained in Chapter 4, this refers to the emergence of another context in thinking about a particular context. In watching the
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video image in the 1st lesson, those who argued against the opinion that CO2 is the cause of global warming listed clouds as the cause of global warming, so Groups B and C were expected to conduct research on clouds. However, the cause of cloud reduction is decreases in dimethyl sulfate, whose cause is the acidification of the sea, and the cause of this is an increase in CO2. Contextual thinking was conducted such that research into the context ‘cloud’ produces the context ‘dimethyl sulfate’, as well as the context ‘sea’, then the context ‘CO2’ in a continuous chain. This also coincides with the analysis from the viewpoint of emergent hypothesis modelling, but the search by Group B in particular formed only a hypothesis. That is, the increase of CO2 is listed as the cause of global warming, but Group B did not provide data on the increase of CO2. Therefore, as a result of Group B’s inquiry, the hypothesis ‘If CO2
increases, global warming is caused by the amount of sunlight (the influence of the sun)’ is formed. In addition, if the increase or decrease of CO2 is examined in the future, the truth or falsehood of this hypothesis is verifiable, and it can thus be said that the premise of the problem-solving process is constructed.
6.2.4 Analysis of teaching experiment from the perspective of ‘emergent hypothesis modelling’
Next, the author analyses the teaching experiment from the viewpoint of ‘emergent hypothesis modelling’. As mentioned above, this viewpoint emerged in conducting the causal inquiry, so the analysis had already been conducted when analysed from the viewpoint of ‘causal inquiry’, but there was a scene where emergent hypothesis modelling appeared prominently. In the presentation by Group D which inquired into the reason argued in the 3rd lesson that CO2 is not the cause of global warming, the following explanation was made using Figure 6-4.
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Figure 6-4. The graph used in Group D’s presentation in the 3rd lesson (with handwritten parts by group D; translated by the author)
Group D: … If carbon dioxide was indeed related to global warming, we suppose that the global temperature would keep rising without lowering. This is why we thought carbon dioxide was not related to global warming.
Figure 6-4 is the supporting figure which Group D found from the Internet.8 Group D regards the fact that the global average temperature is decreasing although CO2 is increasing as evidence, based on which Group D showed that a direct correlation between CO2 and global warming does not exist, so a causal relationship cannot exist. The hypothesis was clearly indicated in the explanation of Group D. It is the hypothesis ‘If carbon dioxide is involved in global warming, then the temperature of the world would continue to rise without falling’. In order to judge whether this hypothesis is correct, Figure 6-4 was used in the discussion. As a result, it was argued that CO2 is not the cause of global warming. Therefore, if it is explained in terms of emergent hypothesis modelling, an anticipation was performed for the original
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problem ‘Is CO2 the cause of global warming or not?’, then the hypothesis model-for ‘The cause of global warming is not CO2’ for Group D was determined, and the search was carried out by contextual thinking on CO2 based on this, and finally, the hypothesis model-of ‘If carbon dioxide is involved in global warming, then the temperature of the world would continue to rise without falling’ emerged. That is, it can be said that the premise of the problem-solving process was established, and then the problem solving itself was also conducted of verifying the hypothesis using Figure 6-4.