On a conjecture for the non-existence of the expectation of randomly stopped sums

1995 ◽  
Vol 32 (4) ◽  
pp. 1138-1141
Author(s):  
Claude Lefèvre ◽  
Sergey Utev

In a recent paper on the validity of Wald's equation, Roters (1994) raised an important question on the non-existence of the expectation of randomly stopped sums. The purpose of this note is to answer the question in the affirmative. As a consequence, an old question by Taylor (1972) also gets a positive answer.


1995 ◽  
Vol 32 (04) ◽  
pp. 1138-1141
Author(s):  
Claude Lefèvre ◽  
Sergey Utev

In a recent paper on the validity of Wald's equation, Roters (1994) raised an important question on the non-existence of the expectation of randomly stopped sums. The purpose of this note is to answer the question in the affirmative. As a consequence, an old question by Taylor (1972) also gets a positive answer.



1965 ◽  
Vol 36 (3) ◽  
pp. 789-799 ◽  
Author(s):  
Y. S. Chow ◽  
Herbert Robbins ◽  
Henry Teicher


Bernoulli ◽  
2008 ◽  
Vol 14 (2) ◽  
pp. 391-404 ◽  
Author(s):  
Denis Denisov ◽  
Serguei Foss ◽  
Dmitry Korshunov




Bernoulli ◽  
2010 ◽  
Vol 16 (4) ◽  
pp. 971-994 ◽  
Author(s):  
Denis Denisov ◽  
Serguei Foss ◽  
Dmitry Korshunov


1966 ◽  
Vol 11 (1) ◽  
pp. 160-165 ◽  
Author(s):  
H. Teicher


1970 ◽  
Vol 7 (1) ◽  
pp. 59-68 ◽  
Author(s):  
W. J. Hall

Various formulas of Wald relating to randomly stopped sums have well known continuous-time analogs, holding in particular for Wiener processes. However, sufficiently general forms of most of these do not appear explicitly in the literature. Recent papers by Robbins and Samuel (1966) and by Brown (1969) provide general results on Wald's equations in discrete time and these are here extended (Theorems 2 and 3) to Wiener processes and other homogeneous additive processes, that is, continuous-time processes with stationary independent increments. We also give an inequality (Theorem 1) related to Wald's identity in continuous time, and we derive, as corollaries of Wald's equations, bounds on the variance of an arbitrary stopping time. The Wiener process versions of these results find application in a variety of stopping problems. Specifically, all are used in Hall ((1968), (1969)); see also Bechhofer, Kiefer, and Sobel (1968), Root (1969), and Shepp (1967).



2016 ◽  
Vol 113 ◽  
pp. 84-93 ◽  
Author(s):  
Svetlana Danilenko ◽  
Jonas Šiaulys


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