Infinitely often and almost always

From Machinelearning
Revision as of 21:16, 31 July 2019 by IssaRice (talk | contribs)

Let A1,A2,A3,… be a sequence of events in some sample space Ω.

perspective infinitely often almost always
unions and intersections ω∈⋂N=1∞⋃n=N∞An ω∈⋃N=1∞⋂n=N∞An
first-order quantifiers ∀N≥1∃n≥N:ω∈An ∃N≤1∀n≥N:ω∈An
verbal expression ω∈An for infinitely many n≥1 ω∈An for almost all n≥1, i.e. ω∈An for all but finitely many n≥1, i.e. ω∉An for finitely many n≥1
lim sup/lim inf ω∈lim supn→∞An ω∈lim infn→∞An
limit of sup/inf ω∈limN→∞supn≥NAn ω∈limN→∞infn≥NAn