Escritoire\Writing\Case\Probability-Expression\IPCC_Likelihood_Scale

The Intergovernmental Panel on Climate Change specifies terms to describe probabilities for use in their reports:

• Virtually certain > 99%
• Very likely > 90%
• Likely > 66%
• About as likely as not 33-66%
• Unlikely < 33%
• Very unlikely < 10%
• Exceptionally unlikely < 1%

As implemented in Pacisco, when entering a rating using the IPCC terms, the probability values used are the middle of the range:

• Virtually certain > 99% = 0.995
• Very likely > 90% = 0.95
• Likely > 66% = 0.78
• About as likely as not 33-66% = 0.495
• Unlikely < 33% = 0.21
• Very unlikely < 10% = 0.05
• Exceptionally unlikely < 1% = 0.005

When calculated responses are displayed, the IPCC terms are assigned as:

• > 0.99 & < 1 is ‘Virtually certain > 99%’
• > 0.9 & <= 0.99 is ‘Very likely > 90%’
• > 0.66 & <= 0.9 is ‘Likely > 66%’
• <= 0.66 & => 0.33 is ‘About as likely as not 33-66%’
• < 0.33 & => 0.1 is ‘Unlikely < 33%’
• < 0.1 & => 0.01 is ‘Very unlikely < 10%’
• < 0.01 & > 0 is ‘Exceptionally unlikely < 1%’

In addition to allow for handling mathematical and logical values:

• 1 is ‘True’
• 0 is ‘False’

Also ‘bad’ ratings can be selected:

• Unrated
• Illogical
• Incoherent
• Irrelevant
• Mendacious