Environmental Decisions in the Face of Uncertainty (2013) / Chapter Skim
Currently Skimming:
6 Communication of Uncertainty
6 Communication of Uncertainty
Pages 181-216
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 181... ...
Although, as discussed in the previous chapters, a number of factors play a role in EPA's decisions, most of the research the committee identified on the communication of environmental decisions focuses on communication of the uncertainty in estimates of human health risk, and those uncertainties are the focus of this chapter. This chapter begins with background information on the communication of those risks.
|
From page 182... ...
In the context of EPA's decisions, stakeholders include the decision makers at the agency, the industries potentially affected by a regulatory decision, and individuals or groups affected by the decision, including local community members for local issues or all the public for issues of national significance. Improving Risk Communication (NRC, 1989)
|
From page 183... ...
Chapter 2 discusses EPA's decisions and supporting documentation around arsenic in drinking water, the Clean Air Interstate Rule (CAIR) , and methylmercury, including the uncertainty analyses that EPA conducted and presented for those regulatory decisions.
|
From page 184... ...
It is important to note that the existence of weaknesses does not necessarily indicate that a given method should not be used, but rather those weaknesses should be considered and adjusted for when developing a communication strategy. Numeric Presentation of Uncertainty In general, numeric presentations of probabilistic information -- such as presenting information in terms of percentages and frequencies -- can lead to more accurate perceptions of risk than verbal and graphic formats (Budescu et al., 2009)
|
From page 185... ...
For example, numeric presentations might be more appropriate for EPA decision makers and stakeholders with technical backgrounds than for stakeholders with less technical backgrounds. As discussed by Peters (2008)
|
From page 186... ...
186 ENVIRONMENTAL DECISIONS IN THE FACE OF UNCERTAINTY BOX 6-1 Strengths and Weaknesses of Numeric, Ver bal, and Visual Communication of Riska Numeric communication of risk (e.g., percentages, frequencies) Strengths Weaknesses • Lacks sensitivity for adequately • s precise and leads to more I tapping into and expressing gut accurate perceptions of level reactions and intuitions risk than the use of prob • People have problems under ability phrases and graphical standing and applying math displays ematical concepts (level of • Conveys aura of scientific numeracy)
|
From page 187... ...
COMMUNICATION OF UNCERTAINTY 187 V isual (graphic) communication of risk (e.g., pie charts, scatter plots, line graphs)
|
From page 188... ...
Such representations may do a better job of capturing people's attention than numeric presentations, and they are also effective for portraying directionality. People are typically familiar with verbal expressions of risk from everyday language (for example, the phrase "It will likely rain tomorrow")
|
From page 189... ...
Qualitative descriptions of probability -- that is, those that include a description or definition for a category of certainty -- are sometimes used instead of such subjective calibrations as "very likely" or "unlikely," which are open for individual interpretation. The third assessment report of the Intergovernmental Panel on Climate Change (IPCC)
|
From page 190... ...
Established but incomplete: Models incorporate most known processes, although some parameterizations may not be well tested; observations are somewhat consistent with theoretical or model results but incomplete; current empirical estimates are well founded, but the possibility of changes in governing processes over time is considerable; or only one or a few lines of evidence support the finding. Competing Explanations: Different model representations account for different aspects of observations or evidence, or incorporate different aspects of key processes, leading to competing explanations.
|
From page 191... ...
. Furthermore, uncertainties about the outcomes of an analysis can also be depicted using graphical displays, such as bar charts, pie charts, probability density functions,2 cumulative density functions,3 and box-andwhisker plots.
|
From page 192... ...
192 ENVIRONMENTAL DECISIONS IN THE FACE OF UNCERTAINTY Picture 1 Picture 5 0 2 4 6 8 10 12 14 16 18 19 INCHES OF SNOW Picture 2 0.25 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 0.20 INCHES OF SNOW Probability 0.15 0.10 Picture 6 0.05 0.00 0–2 2–4 4–6 6–8 8–10 10–12 12–14 14–16 16–18 0 2 4 6 8 10 12 14 16 18 INCHES OF SNOW INCHES OF SNOW Picture 3 Picture 7 7% 10% INCHES OF SNOW 7% 0–2 14% 7% 2–4 0 2 4 6 8 10 12 14 4–6 INCHES OF SNOW 6–8 8% 8–10 10–12 12–14 Picture 8 12% 14–16 35% 0 2 4 6 8 10 12 14 16 18 INCHES OF SNOW Picture 4 Picture 9 0.16 0.14 1.0 Probability Density 0.12 0.9 0.10 0.8 Cumulative Probability 0.08 0.7 0.06 0.6 0.04 0.5 0.02 0.4 0.00 0.3 0 2 4 6 8 10 12 14 16 18 20 0.2 INCHES OF SNOW 0.1 0.0 0 2 4 6 8 10 12 14 16 18 INCHES OF SNOW FIGURE 6-1 Nine displays for communicating uncertain estimates for the value of a single variable used in experiments. Picture 1: point estimate with an error bar; Picture 2: bar chart; Picture 3: pie chart; Picture 4: conventional probability density function; Picture 5: probability density function of half its regular height together with its mirror image; Picture 6: horizontal bar shaded to display probability density using dots; Picture 7: horizontal bar shaded to display probability density using lines; Picture 8: Tukey box plot modified to exclude the maximum and minimum values and to display the mean with a solid point; Picture 9: conventional cumulative distribution function.
|
From page 193... ...
When asked whether probability density functions might create a bias toward tighter spread, almost all participants reported that the probability density function made them inclined to choose the intermediate option. Participants had more difficulty interpreting the cumulative density function, and most of the participants said that the cumulative density function did not help with decision making.6 Participants reported that a graphic that listed the sources of uncertainty and described the impact of each source of uncertainty on the estimates of net benefits (see Figure 6-2)
|
From page 194... ...
a probability density function, (b) a cumulative distribution function, and (c)
|
From page 195... ...
The peak in the curve is the mode, and the shape of 7 Uncertainty along more than one dimension can be graphed using a cumulative distribu tion function, a probability density function, or a box plot using either multiple graphs or superimposing uncertainties along one dimension over another. An alternative is to use error bars within a line graph, where the error bars represent uncertainty, or to use probability surfaces to depict uncertainty three-dimensionally (Krupnick et al., 2006)
|
From page 196... ...
Ibrekk and Morgan (1987) concluded that, until future research suggests another strategy is more effective, it may be best to use both cumulative and probability density functions with the same horizontal scale and with the location of the mean clearly indicated on each.
|
From page 197... ...
are controlled, however, evidence indicates that graphic displays lead to greater risk aversion than numerical presentations (Slovic and Monahan, 1995; Slovic et al., 2000)
|
From page 198... ...
. Framing Biases One line of risk perception research that is relevant to EPA's communication of uncertainty is the study of the effects that alternative ways of framing risk information have on risk perception and decision making.
|
From page 199... ...
8 and the Netherlands Environmental Assessment Agency have developed guidance on communicating uncertainty (Kloprogge et al., 2007)
|
From page 200... ...
Decision Context To develop guidance on communicating uncertainty, the Netherlands Environmental Assessment Agency relied on literature reviews, a workshop on uncertainty communication, and research by the authors of the guidance document (Kloprogge et al., 2007)
|
From page 201... ...
explicitly including the communication of uncertainties in emergency plans can help facilitate communications when an environmental crisis requiring an emergency response occurs. Given the need for a quick decision and the large amount of uncertainty that often occurs in emergency situations, it is important that communication strategies include plans to collect information that might reduce uncertainties or plans to revisit the decision once more data are gathered.
|
From page 202... ...
, and those subgroups that are more at risk should be identified during the problem-formulation phase, and discussions about potential uncertainties should be initiated during that phase. The Type and Source of the Uncertainty Some research indicates that, when communicating uncertainties in the results of risk assessments to decision makers, it is valuable to be specific about the nature or types of the uncertainties.
|
From page 203... ...
Knowing who is likely to be affected by the uncertainty in the costs and benefits would allow decision makers to design the initial proposed regulations to address or prepare for those potential outcomes in advance. If the individual sources of uncertainty that contribute to the overall uncertainty can be determined, then uncertainty analyses in, for instance, cost– benefit analyses or cost-effectiveness analyses could incorporate graphic representations displaying the relative importance of the different sources of uncertainty sequentially so as to provide an easily interpretable graphic display of the sources of uncertainty (Krupnick et al., 2006)
|
From page 204... ...
That would provide summary information for all audiences as well as further details of the uncertainty analyses for technical audiences or others with an interest in seeing all the details. Biases Uncertainty information concerning probabilities has been found to be susceptible to biases by both experts and non-experts (Hoffrage et al., 2000; Kloprogge et al., 2007; Slovic, 2000; Slovic et al., 1979, 1981; Tversky and Kahneman, 1974)
|
From page 205... ...
. A second bias that can influence the communication of health risks and their uncertainties is confirmation bias.
|
From page 206... ...
and about balance in representation of opinions, but journalists vary widely in their backgrounds, technical expertise, and ability to accurately report and explain environmental decisions. Even those who cover environmental policy making will not necessarily be familiar with the details of risk assessment and its inherent uncertainties, making it challenging to convey the rationale for decisions based, in part, on those assessments.
|
From page 207... ...
It is important to remember, however, that there are reasons to communicate uncertainties beyond the potential to increase social trust (Stirling, 2010)
|
From page 208... ...
Thus engaging the public and policy makers, in addition to scientists, in the process of health risk assessments not only improves the assessment, but can also increase both trust in the process and communications about health risks by allowing the perspectives of all stakeholders to inform the assessment. Frewer and Salter (2002)
|
From page 209... ...
. KEY FINDINGS • Although communication is often thought of in terms of commu nication to an audience, two-way conversations about risks and uncertainties throughout the decision-making process are key to the informed environmental decisions that are acceptable to stake holders.
|
From page 210... ...
Often a combination of numeric, verbal, and graphic displays of uncer tainty information may be the best option. In general, however, the most appropriate communication strategy for uncertainty depends on o decision context; the o purpose of the communication; the o type of uncertainty; and the o characteristics of the audience, including the level of techni the cal expertise, personal and group biases, and the level of social trust.
|
From page 211... ...
Risk Analysis 28(1)
|
From page 212... ...
2005. Regulatory impact analysis for the final Clean Air Interstate Rule.
|
From page 213... ...
the competition. Organizational Behavior and Human Decision Processes 103(2)
|
From page 214... ...
Organizational Behavior and Human Decision Processes 66(1)
|
From page 215... ...
Or ganizational Behavior and Human Decision Processes 90(1)
|
From page 216... ...
2008. Uncertainty communication in environmental assessments: Views from the Dutch science policy interface.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.