Does Showing F(x+1/n)--->F(x) Prove Continuity to the Right for Any Sequence?

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Discussion Overview

The discussion revolves around the concept of continuity to the right for the repartition function F, specifically examining whether the convergence of F(x + 1/n) to F(x) is sufficient to establish continuity for any sequence converging to x from the right. The scope includes theoretical aspects of continuity in probability functions.

Discussion Character

  • Debate/contested

Main Points Raised

  • One participant questions whether proving F(x + 1/n) converges to F(x) is sufficient for continuity to the right for any sequence converging to x, suggesting that continuity to the right should apply to any sequence {a_n} in (x, +∞).
  • Another participant agrees that if the proof relies solely on the convergence of the sequence to zero, then it should not depend on the specific choice of 1/n as an example.
  • A later reply indicates that the increasing nature of the function F allows the proof to extend beyond the 1/n sequence, implying that the properties of increasing functions support the argument.
  • Further clarification is provided that since F is increasing, values of F for points between 1/n and 1/(n+1) must also fall between F(1/n) and F(1/(n+1), suggesting that the epsilon/delta argument for the 1/n sequence applies to other sequences converging to zero.

Areas of Agreement / Disagreement

Participants express differing views on whether the convergence of F(x + 1/n) to F(x) is sufficient for continuity to the right for any sequence. While some acknowledge the increasing nature of F as a factor that may support the argument, there is no consensus on the sufficiency of the proof for all sequences.

Contextual Notes

The discussion highlights the potential limitations of the proof's reliance on the specific sequence 1/n and the implications of the increasing property of the function F. There is an unresolved consideration regarding whether the argument holds for all sequences converging to x.

quasar987
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My probability professor proved the property of "continuity to the right" of the repartition function F by showing that F(x+1/n)--->F(x). But as I remember it, continuity to the right means that for any sequence {a_n} of elements of (x,+infty) that converges to x, F(a_n) converges to F(x). Is there some subtlety I'm not aware of by which showing F(x+1/n)--->F(x) is sufficient to show it works for any sequence?
 
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Well, you are right.
If your professor's proof is correct, then his proof cannot essentially rely on other properties of the 1/n-sequence than that it converges to zero; i.e, that is, it is only the DISTANCE a given point x+1/n has from x that is relevant in the actual proof.

It might be that it is easiest to use 1/n as an EXAMPLE of a sequence, but the proof shouldn't crucially rest upon that particular choice.
 
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He agreed (by email) that it is insufficient to prove it for 1/n in the case of any function, but because the partition function F(x) is an increasing function, it is sufficient. Do you see why?
 
Okay, note that since F is INCREASING, it means that the function values for any points squeezed in between 1/n and 1/(n+1) must be squeezed in between the function values F(1/n) and F(1/(n+1)).
Thus, any epsdilon/delta squeeze valid for the 1/n sequence must be valid for any other sequence converging to 0 as well, since its terms are necessarily squeezed in between the harmonic sequence terms.
 
I see it thanks.
 

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