Final Words on Making Great Evidence

In the last two newsletters, we've talked about Credibility and Social Consensus as evidence to answer questions that are asked about claims made in the course of a work discussion. FINALLY we are going to talk about the third and final category of evidence. REAL evidence, that is to say Objective Evidence, means evidence that can be examined and reviewed. Something tangible like data, numbers, testimony, physical articles all qualify as objective evidence. By the way, it doesn’t mean that the evidence itself is objective in content, just that it is tangible (an object) and can be examined by more than one examiner.


Objective evidence is often meant to represent something; that is to serve as an example. Sometimes, a sample will be offered to (like a cracker with cheese on it in a supermarket) and it is offered as objective evidence that this cheese and cracker is representative of the cheese and crackers YOU’LL enjoy if you buy the product. We all know that sometimes this is true and sometimes not. Objective evidence should be subjected to tests in order to determine its validity. Tests for objective evidence are:

• Are the examples representative? OR, were they selected to show certain desirable characteristics?
• From a large enough range? OR, taken from just a few places in the population?
• Are they selected randomly? OR, do they all come from a specific place in the population?
• Is the sample size large enough? OR, were just a few samples taken?
• Are there counterexamples? THAT IS, are there a meaningful number of samples that show opposite characteristics?
• Are the statistics properly prepared? THAT IS, using standard (or logical) statistical techniques?
• Are the objects and testimony authentic? OR, are they fraudulent or modified?

So now we have covered the three kinds of evidence. Let’s talk a little more on how to weigh it. Generally, evidence reported first-hand (by an involved party) is better than second-hand (by a party that was not personally involved, but heard something from someone that was). That doesn’t mean that first-hand evidence is always right or second-hand always wrong, just that GENERALLY, one is better than the other. Also, opinions offered by an expert are GENERALLY better than those of a layperson. The six grades of evidence are as follows (lowest to highest):

1. Assertion (a personal opinion is not very strong by itself)
2. Common Knowledge or Stipulation (meaning there is social consensus regarding an opinion)
3. Lay Opinion (if a reasoned conclusion, meaning there has been some reasoned analysis and there is some credible backing)
4. Expert Opinion or Consensus of Lay Opinion (Expert opinions are backed by the expert’s credibility. A consensus of reasoned conclusions by multiple lay people is as good)
5. An Empirical Study or Consensus of Expert Opinion
6. Consensus of Studies

Now we know how to make a claim, ask the important questions, what evidence to expect to be offered, and how to test it and weight it. It is very important to know that the evidence brought to a discussion is good enough to consider.

Often though, even though the evidence is good evidence (the numbers are right and add up, or the testimony is truthful), it doesn’t actually support the claim. This is one of the biggest problems in these kinds of discussions. Someone says that “sales are down because the economy is bad” and then presents a bunch of evidence that proves the economy is bad, but never actually proves that the economy is why sales are bad.

Next we will talk about the various ways to determine how well the evidence supports the claim, and learn how to make our arguments more robust and “unbreakable”.


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