Step 5 Identifying probable causes for the Truckee

Step 5: Identifying probable causes for the Truckee River case study

Detect or Suspect Biological Impairment Stressor Identification Define the Case List Candidate Causes Decision-maker and Stakeholder Involvement Evaluate Data from the Case Evaluate Data from Elsewhere As Necessary: Acquire Data and Iterate Process Step 5: Identify Probable Cause Identify and Apportion Sources Management Action: Eliminate or Control Sources, Monitor Results Biological Condition Restored or Protected 2

Weighing the evidence for each candidate cause • Evaluate the quantity & quality of evidence • Evaluate consistency & credibility • Summarize the compelling evidence 3

Things to keep in mind when scoring… • Be consistent across candidate causes • Don’t double-count data • Think about the quality & quantity of the data you’re using • Document your thought process 4

The scoring system R refutes D diagnoses +++ convincingly supports (or weakens - - -) ++ strongly supports (or weakens - -) + somewhat supports (or weakens - ) 0 neither supports nor weakens NE no evidence 5

Let’s start scoring each type of evidence, across each candidate cause… 6

Evaluate quantity & quality of evidence • Quality & quantity of data influence scores • Now evaluate overall quality of evidence • Lots of consistent evidence reduces quality concerns for any 1 type of evidence • Poor quality data may be discounted • Consider study designs, methods, relevance, variability, & other QA issues 7

Now that we’ve scored each type of evidence, let’s evaluate consistency & credibility 8

Evaluate consistency & credibility • Prepare summary table of scores • Do not add up scores! • Evaluate consistency of evidence • Look for compelling evidence • If evidence is inconsistent, consider mechanistic explanations – e. g. , lab data not consistent with field conditions due to differing bioavailability 9

Scoring consistency & credibility Consistency of Evidence All available types of evidence support the case for the candidate cause. +++ All available types of evidence weaken the case for the candidate cause. --- All available types of evidence support the case for the candidate cause, but few types are available. + All available types of evidence weaken the case for the candidate cause, but few types are available. - The evidence is ambiguous or inadequate. 0 Some available types of evidence support and some weaken the case for the candidate cause. - There is a credible explanation for any negative inconsistencies or ambiguities in an otherwise positive body of evidence that could make the body of evidence consistently supporting. Explanation of the Evidence ++ There is no explanation for the inconsistencies or ambiguities in the evidence. 0 There is a credible explanation for any positive inconsistencies or ambiguities in an otherwise negative body of evidence that could make the body of evidence consistently weakening. 10

Summarize compelling evidence • • Make an overall evaluation of strength of evidence for each candidate cause – what evidence compels belief that candidate cause induced effect? – what evidence strongly casts doubt? Consider the principle characteristics of causal relationships – these are what you’re trying to show – they summarize the 15 types of evidence 11

What comes after causal analysis? • If confidence in results is low… plan studies to obtain critical evidence – experimental studies most likely to be convincing – • If confidence in results is high… identify sources – take action – monitor results – 12

So – what’s next? • Additional data to collect? • Additional analyses to conduct? • Additional sites to consider? • Outreach & communication? 13