A second set of tests was conducted in exploration of the effectiveness of water saving devices in the participants’ homes. This time the comparison was made between the water consumption before the installation of devices and consumption after for each participant and non-participant. Again, the analysis had two phases. In the first phase households in the same areas were grouped together to form three separate datasets so that programme effectiveness could be evaluated on the area level. In the second phase all households were analysed together so that the effectiveness of the programme as a whole could be explored. Normality tests were conducted prior to the analysis so that a choice between non parametric tests and the related samples T-test could be made, since related samples T-test is not suitable for non-normal samples. It is worth noting that for this before-after comparison, the value that should be assessed for normality is the difference between the ‘before’ and the ‘after’ value (Field, 2013) and not the consumption values themselves.
RESULTS FOR HOUSEHOLDS IN BEDFORD, WELLINGBOROUGH, MILTON KEYNES AND NORTHAMPTON
After outliers’ removal, the remaining set of households for each of these areas was small. But due to their proximity, these areas experienced almost the same weather conditions. This allowed for them to be grouped together to form a sample of 17 participating households and 37 not-participating ones. The sample still remained small, thus normality tests were conducted so that the choice between running a related samples T-test or non-parametric tests could be made.
Consumption difference for participants appeared to be normal since both tests were non- significant. However the same does not apply for the non-participants’ sample since Shapiro-Wilk test was significant (see Figure A9 & A10). Therefore, non-parametric Related Samples Wilcoxon Signed Rank test was preferred for the analysis.
For the participants in the wider Bedford area, water consumption was significantly lower after the installation of devices period, T=17, p=0.003<0.05 (Table A5-Appendix). This interpretation is based on the fact that negative differences prevail in the test results and
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is further illustrated in Figure 4.18. The mean consumption for the sample of participants was 312 l/hh/d and 264.94 l/hh/d before and after the installation of the water saving devices respectively.
Figure 4.18 Participants' Consumption for the period before and after the programme launch in Bedford, Wellingborough, Milton Keynes and Northampton area (n=17)
For non-participants, water consumption differed significantly between the two periods, T=460, p=.046<.05 (Table A6-Appendix). Most probably, water consumption for the non-participants group increased after the period of the devices installation since positive differences prevail in the test results. This is further illustrated in the following Figure and it may be due to the observed maximum temperature increase during the period after programme launch (see Figure 4.10). The mean consumption for the sample of non- participants was 237.77 l/hh/d and 246.82 l/hh/d before and after the installation of the water saving devices respectively.
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Figure 4.19 Non-Participants' Consumption for the period before and after the programme launch in Bedford, Wellingborough, Milton Keynes and Northampton area (n=37)
RESULTS FOR HOUSEHOLDS IN COLCHESTER AND IPSWICH
After outliers’ removal, the remaining set of households for each of these areas was small. But due to their proximity, these areas experienced almost the same weather conditions. This allowed for them to be grouped together to form a sample of 17 participating households and 37 not-participating ones. The sample still remained small, thus normality tests were conducted so that the choice between running a related samples T-test or non-parametric tests could be made. Results for both samples point out that both water consumption difference distributions approach the normal distribution (Figure A11 & A12), therefore Paired samples T-test was used for the analysis (Table A7).
The T-test suggests that on average there was not a significant change in consumption between the two periods t(16)=1.92, p=.073. Participants consumption before the installation period was not significantly different (M=268.26, SE=32.6), than after (M=260.48, SE=32.6) although there are signs of possible decrease. The bootstrapped confidence intervals [.39, 15.1] support the notion that water consumption may have changed after the devices installation period, since the interval does not contain zero. It is rather implied that consumption had decreased slightly after the installation period, since only positive numbers appear in the confidence interval. This is further illustrated in Figure 4.20. The mean consumption for the sample of participants was 268.3 l/hh/d and
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260.5 l/hh/d before and after the installation of the water saving devices respectively.
Figure 4.20 Participants' Consumption for the period before and after the programme launch in Colchester-Ipswich area (n=17)
The T-test (Table A8-Appendix) demonstrates that for the non-participants there was a significant change in consumption between the two periods t(36)=-2.45, p=.019. Non- Participants consumption before the installation period was significantly lower (M=243.1, SE=20.1), than after (M=250.39, SE=20.75).
Figure 4.21 Non-Participants' Consumption for the period before and after the programme launch in Colchester-Ipswich area (n=37)
The bootstrapped confidence intervals [-13.52, -1.13] support the notion that water consumption did change after the devices installation period, since the interval does not
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contain zero. It is rather implied that consumption increased slightly after the installation period, since only negative numbers exist in the confidence interval. This is further illustrated in Figure 4.21. The mean consumption for the sample of non-participants was 243.08 l/hh/d and 250.4 l/hh/d before and after the installation of the water saving devices respectively.
RESULTS FOR HOUSEHOLDS IN GRIMSBY
After outliers’ removal, the remaining set of households for this area was small, thus normality tests were conducted so that the choice between running a paired samples T- test or non-parametric tests could be made.
The participants sample distribution differs significantly from the normal distribution. For the non-participants sample the two tests do not agree, however the Shapiro-Wilk test is more robust with samples of less than 50 entries and since it is significant we can conclude that the sample does not follow a normal distribution (see Figure A13 & A14). Thus non-parametric tests should be preferred over paired samples T-test.
For participants, water consumption did not differ significantly between the two periods based on the Wilcoxon Signed Rank test (Table A9-Appendix), T=7, p=.123>0.05. However, there is a sign that consumption of the participating households may have decreased after the programme launch period, since negative differences prevail in the results. This is further illustrated in Figure 4.22. The mean consumption for the sample of participants was 196.4 l/hh/d and 164.9 l/hh/d before and after the installation of the water saving devices respectively.
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Figure 4.22 Participants' Consumption for the period before and after the programme launch in Grimsby area (n=8)
As the Related samples Wilcoxon Signed Rank test suggests (Table A10-Appendix), water consumption was not significantly different after the installation of devices period for the sample of non-participants: T=107, p=0.629>0.05. However, it is implied that water consumption may have increased over the programme implementation period since positive differences prevail in the test results. This is further illustrated in Figure 4.23. The mean consumption for the sample of non-participants was 234.98 l/hh/d and 241.79 l/hh/d before and after the installation of the water saving devices respectively.
Figure 4.23 Non-Participants' Consumption for the period before and after the programme launch in Grimsby area (n=19)
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Figure 4.24 Participants' consumption for the period before and after the programme launch (l/hh/d) (n=42)
RESULTS FOR ALL AREAS
Aggregating all areas samples into a participants and a non-participants sample provides a sample of 63 participating households and non-participating ones. Normality tests were conducted so that the choice between running a paired samples T-test or non-parametric tests could be made. Tests for the significance of consumption change were conducted both for aggregated (l/hh/d) and per capita consumption values.
The distribution of the participants sample was significantly non normal both for l/hh/d and per capita values (see Appendix). Thus, Non parametric tests were used. The normality tests for the non-participants sample are significant, suggesting that the distribution deviates from normality. However, the big sample size (N=92>50) allows for the paired samples T-test to be accurate enough. Thus, paired samples T-test will be used for the non-participants sample analysis. For participants, aggregated water consumption differed significantly between the two periods based on the Wilcoxon Signed Rank test, T=566, p=.002<0.05 (Table A11-Appendix). Most probably, water consumption for the participants group decreased after the period of the devices installation since negative differences prevail in the test results. This is further illustrated in Figure 4.24. The mean consumption for the sample of participants was 272.58 l/hh/d and 250.23 l/hh/d before and after the installation of the water saving devices respectively.
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As far as per capita consumption is concerned, it differed significantly between the two periods based on the Wilcoxon Signed Rank test (Table A12-Appendix), T=523, p=.001<0.05. Most probably, water consumption for the participants group decreased after the period of the devices installation since negative differences prevail in the test results. This is further illustrated in Figure 4.25.
Figure 4.25 Participants' per Capita Consumption for the period before and after the programme launch (n=42)
The mean consumption for the sample of participants was 123.27 l/capita/d and 108.10 l/capita/d before and after the installation of the water saving devices respectively.
For the non-participants, the T-test (Table A13-Appendix) illustrates that on average there was a significant change in consumption between the two periods t(91)=-2.88, p=0.005<.05. The test was significant.
Non-Participants’ consumption before the installation period was significantly different (M=239.3, SE=11.75), than after (M=247.22, SE=12.58) and there are definite signs of increase. The bootstrapped confidence intervals [-12.92, -2.51] support the notion that water consumption changed significantly after the devices installation period, since the interval does not contain zero. Also, it is implied that consumption increased after the installation period, since negative numbers prevail in the confidence interval. This is further illustrated in the following figure. The mean consumption for the sample of non- participants was 239.33 l/hh/d and 247.22 l/hh/d before and after the installation of the
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Figure 4.26 Non-Participants' Consumption for the period before and after the programme launch (n=92)