I am reading a great book “Principles.” of Dalio, Ray
There's a paraphrase called “Make believability-weighted decisions.”

“• Make believability-weighted decisions.
My painful mistakes shifted me from having a perspective of “I know I’m right” to having one of “How do I know I’m right?” They gave me the humility I needed to balance my audacity. Knowing that I could be painfully wrong and curiosity about why other smart people saw things differently prompted me to look at things through the eyes of others as well as my own. That allowed me to see many more dimensions than if I saw things just through my own eyes. Learning how to weigh people’s inputs so that I chose the best ones — in other words, so that I believability weighted my decision making — increased my chances of being right and was thrilling. At the same time, I learned to:”

I searched and found that there's no such a word 'believability'.
In dictionary.com, it implies that 'believability' is synonymous with 'credibility'.

Additionally, I search the verb meaning of weight

Verb 1 If you weight something, you make it heavier by adding something to it, for example in order to stop it from moving easily.
Verb 2 If you weight things, you give them different values according to how important or significant they are.

I guess 'weight' is 'verb 1' of 'make it heavier by adding something to it'

In conclusion, “Make believability-weighted decisions.” is “Make credibility-biased decisions.”

Honestly, I didn't understand the author's intention throughly.

Why he labored to invent 'believability' instead of 'credibility', especially he applied the phrase 'believability weighted' as a whole for a verb in 'I believability weighted my decision making'.


1) In English,typically, certain items are said to be weighted in certain situations. So, if you are asking the same questions of 12-year-old kids and 8-year-old kids, you would let the 8-year-old kids make more mistakes since they know less.

the Collins says this: Allowance or adjustment made in order to take account of special circumstances or compensate for a distorting factor.

‘each score is then multiplied by the appropriate weighting, giving a weighted score’

2) x-weighted decision.

In the link given here for a weighted decision matrix, you can look at the chart and see the weighting factors. There is also decision theory that enters into this. Weighting here means assigning factors of importance to a decision, whatever it might be.

3) Believability-weighted decisions are thus ones that have been assigned a certain number of factors to which a number is associated. In this context, the authors is taking inputs from people and assigning a weight to them in making his decision(s).

  • Is a person's input believable or not? [Weighting factor: 5]
  • Is a person's input understandable or not? [Weighting factor: 3]
  • Is a person's input coming from him/her or not? [Weighting factor: 2]

4) How to compute using weighting factors:

statistics and a weighting factor example with student's grades

Your author is using the term in this sense though s/he may not mean it technically. It's origin is technical. S/he is not accepting input without question. The input(s) are being weighted before they are part of her/his decision making.

  • So Believability is credibility, not only the noun of believable here.
    – AbstProcDo
    Feb 6 '18 at 1:17
  • 1
    Something is believable or not. For instance: It is not believable (or credible, same thing) that there are little green aliens having coffee at the local coffee shop. The believability of that statement is very low, probably zero. :).
    – Lambie
    Feb 6 '18 at 16:05

Firstly, believability is listed as the noun form of believable on dictionary.com, and broadly means the same as credibility, as you've rightly pointed out.

Secondly, you're quite correct in terms of weighted meaning the same as biased, in this context. That said, the use of weighted instead of biased is partly a matter of preference, partly semantics. While they mean the same thing, they carry different connotations to a typical reader.

When read with a non-scientific/mathematical mindset, bias can carry a connotation of favouritism, whereas weighted doesn't. Of course, in a scientific or mathematical context, there are no such connotations, and bias is a commonly used word.

Finally, using such a phrase as a verb is called conversion or verbification. While it has attracted criticism, there are cases where it has entered mainstream use since it helps make sentences more compact (e.g. as much as Google hates its use as a verb, "Google it" is easier to say/type than "Search for it on Google").

On a lighter note, Bill Watterson's comic strip about Calvin and Hobbes had this gem: Calvin and Hobbes Strip - 25-Jan-1993 - Verbing weirds language Image credit: http://www.gocomics.com/calvinandhobbes/1993/01/25


I would differ and suggest that "believability-weighted decisions" uses the second meaning of "weight", that is, give things different values according to how important or significant they are, and definitely not biased.

This is based on the phrase "how to weigh people’s inputs".

The text suggests that the author decides between inputs based (at least in part) on how believable they are, such that more believable inputs weigh more than less believable inputs.

The term believability is a typical grammatical compound-word-invention for a quality of something being passively possible to do; just as something that can be depended on is dependable and has a quality of dependability, one could refer to answerability of questions, combilability of code, and translatability of text - all of which aren't recognized by my spell checker, but their understandability is undoubtable!

More seriously, Wiktionary contains several examples of the suffix -abilty that you might consider "invented". The Macmillan dictionary also describes this suffix as used with adjectives ending in ‘-able’ to make nouns meaning a particular quality - which is applicable to the word "believable".


"Credibility" is often about the history of the source being correct, rather than whether a particular idea is correct.

"Plausibility" is about whether a particular idea might possibly be correct.

"Believability" is somewhere between "credibility" and "plausibility". It has "plausibility"'s focus on the idea (instead of the source). It has the implication of "if I think about it, does this seem very likely to be true", instead of "plausibility"'s "it could possibly be true."

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