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Equation 4 · Part 7 · Comparing the Main Approaches to Origins of Life and Astrobiology

addition

P(Hbio∣D)=P(D∣Hbio) P(Hbio)P(D∣Hbio) P(Hbio)+P(D∣Hab) P(Hab)P(H_{bio} \mid D) = \frac{P(D \mid H_{bio})\, P(H_{bio})}{P(D \mid H_{bio})\, P(H_{bio}) + P(D \mid H_{ab})\, P(H_{ab})}
addition

What this part means

Add the term after the plus sign to the term or group before it.

Its job in the formula

Add the term after the plus sign to the term or group before it.

The passage around this formula

What lets these three very different kinds of evidence be compared at all is a shared logical structure that the Astrobiology community has tried to formalize explicitly rather than leave implicit. David Catling and coauthors proposed treating a biosignature detection as a Bayesian inference problem: a prior probability that a given planet or sample harbors life, updated by the likelihood of the observed data under a “life” hypothesis versus under one or more specific abiotic alternative hypotheses, yields a posterior probability rather than a binary yes-or-no verdict [ 7 ] . Written compactly, for a single candidate abiotic alternative HabH_{ab} competing with a life hypothesis HbioH_{bio} given…

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Learn the underlying idea

Addition combines quantities; subtraction measures the signed difference between them. Parentheses show what is combined before the rest of the expression is evaluated.

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Sources cited in the surrounding passage

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