Difference between revisions of "Likelihood"
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Most commonly, likelihood can be quantified by statistical analysis. The likelihood of weather events occuring, for instance, has been the subject of a long and well-established study and knows a high degree of statistical basis. Wherever statistical data can predict the future, likelihood can be interpreted to equal [[probability]]. |
Most commonly, likelihood can be quantified by statistical analysis. The likelihood of weather events occuring, for instance, has been the subject of a long and well-established study and knows a high degree of statistical basis. Wherever statistical data can predict the future, likelihood can be interpreted to equal [[probability]]. |
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| − | A precondition for statistical analysis to be valid is that the future can be predicted on the basis of events in the past and this does not hold for all situations. |
+ | A precondition for statistical analysis to be valid is that the future can be predicted on the basis of events in the past and this does not hold for all situations. Particularly in security analysis the use of statistical analysis for the determination of likelihood is highly debatable, as: |
| + | * the likelihood of occurance is influenced by the vulnerability (Compare the risk of flooding with the risk of burglary: whereas the likelihood of high water occuring is indepent of dykes being erected, the likelihood of a burglary attempt occuring at a building depends on the doors having visible locks or not). |
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| + | * the likelihood is influenced by external factors (measures taken by a neighbour can influence the likelihood for burglary for me (waterbed effect)) |
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| + | * the likelihood is influenced by rational beings, who can act against trends. (a criminal will actively look for the weakest link, irrespective of choices made in the past - if the last three attacks where (unsuccessful) hostage takings, is that an indication that the next one will also be a hostage taking, or is it likely that the next one will be a different attack method?) |
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| + | * some forms of crime know a very low rate of occurance, which is a problem for the validity of statistical analysis. |
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| − | =For non-intentional threats= |
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| − | Equals [[probability]]. |
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| − | =For Human intent= |
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Revision as of 10:02, 4 December 2012
Likelihood is the expected plausibility of an event to realise.
Description
Likelihood is one of the defining elements of risk. Usually expressed in the form of probability, it determines, alongside vulnerability and impact, the chance of an unwanted situation occuring.
Most commonly, likelihood can be quantified by statistical analysis. The likelihood of weather events occuring, for instance, has been the subject of a long and well-established study and knows a high degree of statistical basis. Wherever statistical data can predict the future, likelihood can be interpreted to equal probability.
A precondition for statistical analysis to be valid is that the future can be predicted on the basis of events in the past and this does not hold for all situations. Particularly in security analysis the use of statistical analysis for the determination of likelihood is highly debatable, as:
- the likelihood of occurance is influenced by the vulnerability (Compare the risk of flooding with the risk of burglary: whereas the likelihood of high water occuring is indepent of dykes being erected, the likelihood of a burglary attempt occuring at a building depends on the doors having visible locks or not).
- the likelihood is influenced by external factors (measures taken by a neighbour can influence the likelihood for burglary for me (waterbed effect))
- the likelihood is influenced by rational beings, who can act against trends. (a criminal will actively look for the weakest link, irrespective of choices made in the past - if the last three attacks where (unsuccessful) hostage takings, is that an indication that the next one will also be a hostage taking, or is it likely that the next one will be a different attack method?)
- some forms of crime know a very low rate of occurance, which is a problem for the validity of statistical analysis.
For this reason, probability is sometimes subtituted with attractiveness becauses of the problems with the use of probability in determining the likelihood of human intent.
