## Step 5: Identify Probable Causes

Types of evidence

### Consistency of Evidence

#### Concept

Confidence in the argument for or against a candidate cause is increased when many types of evidence consistently support or weaken it.

#### Examples

Consider increased water temperature as a candidate cause of reduced abundance of fish. What findings support or weaken the case for increased temperature as the cause, in terms of consistency of evidence?

• Supporting evidence: Seven types of evidence were available and all support the case for increased temperature as the cause; no evidence weakens the case.
• Weakening evidence: Four types of evidence support the case for increased temperature, but three types of evidence weakened it.
Table 5-6. Consistency of Evidence. A candidate cause is strongly supported if all available types of evidence are consistently supportive. It is greatly weakened if all available types of evidence are consistently weakening. It is weakened if some types of evidence support and others weaken the candidate cause.

#### How do I analyze consistency?

After assembling all the scored types of evidence for a candidate cause, observe if all types of evidence are supporting, weakening, or a mixture of points that support and weaken the case for the candidate cause. Ambiguous evidence (scores of 0) are not included. Based on this assessment, score the body of evidence for that candidate. Keep in mind that is not appropriate to add the plus and minus symbols from the scoring tables to determine consistency.

• Example analysis worksheets for consistency of evidence (from the Little Scioto River, OH, USA):

#### What evidence would support or weaken the case for a candidate cause, in terms of consistency?

Supports

• All types of evidence support the case for the candidate cause.

Weakens

• All types of evidence weaken the case for the candidate cause.
• Some types of evidence support and some weaken the case for the candidate cause, thereby undermining confidence in it as a true cause.

#### How do I score the consistency of evidence?

Finding Interpretation Score
All available types of evidence support the case for the candidate cause. This finding convincingly supports the case for the candidate cause. + + +
All available types of evidence weaken the case for the candidate cause. This finding convincingly weakens the candidate cause. - - -
All available types of evidence support the case for the candidate cause, but few types are available. This finding somewhat supports the case for the candidate cause, but is not strongly supportive because coincidence and errors may be responsible. +
All available types of evidence weaken the case for the candidate cause, but few types are available. This finding somewhat weakens the case for the candidate cause, but is not strongly weakening because coincidence and errors may be responsible. -
The evidence is ambiguous or inadequate. This finding neither supports nor weakens the case for the candidate cause. 0
Some available types of evidence support and some weaken the case for the candidate cause. This finding somewhat weakens the case for the candidate cause, but is not convincing because a few inconsistencies may be explained. -