Redigerer Odds

I [[sannsynlighetsteori]] og [[statistikk]] er '''odds''' for en [[begivenhet (sannsynlighetsteori)|begivenhet]] lik [[sannsynlighet]]en for at begivenheten inntreffer dividert på sannsynligheten for at begivenheten ikke inntreffer. Matematisk er odds lik ''p''&nbsp;/&nbsp;(1&nbsp;−&nbsp;''p''), der ''p'' er sannsynligheten for at begivenheten skal inntreffe. For eksempel, hvis man velger en [[tilfeldig variabel|tilfeldig]] ukedag, så er oddsen for at man velger søndag lik 1/6 (ikke 1/7). [[Logaritme]]n til oddsen kalles [[logit]].<ref>{{Kilde www|url=https://www.wikihow.com/Calculate-Odds|tittel=How to Calculate Odds: 11 Steps (with Pictures)|besøksdato=2023-04-16|språk=en|verk=wikiHow}}</ref>

Odds har i lang tid vært den normale måten å representere sannsynligheter på blant [[bookmaker]]e, selv om måten oddsen presenteres på varierer. Utbetalingsodds er basert på "odds mot" resultatet det tippes på, dvs. (1-p)/p (lik "odds for" et resultat som ikke gir gevinst), men bookmakeren har justert denne litt ned i forhold til sine forventninger for å sikre ham eller henne forventet gevinst på veddemålet.

Oddsselskaper i [[Norge]] kontrolleres av [[Lotteritilsynet]]
<!--Taking an event with a 1 in 5 probability of occurring (i.e. 0.2 or 20%), then the odds are 0.2&nbsp;/&nbsp;(1&nbsp;−&nbsp;0.2) = 0.2&nbsp;/&nbsp;0.8 = '''0.25'''. If you [[Fixed-odds gambling|bet]] 1 at fair odds and the event occurred, you would receive back 4 plus your original 1 stake. This would be presented in [[Fixed-odds gambling#Fractional odds|fractional odds]] of 4 to 1 ''against'' (written as 4&nbsp;:&nbsp;1 or 4/1), in [[Fixed-odds gambling#Decimal odds|decimal odds]] as 5.0 to include the returned stake, in [[craps]] payout as 5 for 1, and in [[Fixed-odds gambling#Moneyline odds|moneyline odds]] as +400 representing the gain from a 100 stake.

By contrast, for an event with a 4 in 5 probability of occurring (i.e. 0.8 or 80%), then the odds are 0.8&nbsp;/&nbsp;(1&nbsp;−&nbsp;0.8) = '''4'''.  If you bet 4 at fair odds and the event occurred, you would receive back 1 plus your original 4 stake. This would be presented in fractional odds of 4 to 1 ''on'' (written as 1&nbsp;:&nbsp;4 or 1/4), in decimal odds as 1.25 to include the returned stake, in craps as 5 for 4, and in moneyline odds as −400 representing the stake necessary to gain 100.

The odds are a [[ratio]] of probabilities; an [[odds ratio]] is a ratio of odds, that is, a ratio of ratios of probabilities.  Odds-ratios are often used in analysis of [[clinical trial]]s.  While they have useful mathematical properties, they can produce counter-intuitive results: in the example above an 80% probability is four times the chance of a 20% probability but the odds are 16 times higher.-->

==Se også==
*[[Bookmaker]]
*[[Sannsynlighetsteori]]
*[[Statistikk]]
*[[Gambling]]

== Referanser ==
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[[Kategori:Tilfeldighet]]
[[Kategori:Statistiske forhold]]
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