  The jaggedness of an order ideal I in a poset P is the number of maximal
elements in I plus the number of minimal elements of P not in I. A probability
distribution on the set of order ideals of P is toggle-symmetric if for every p
in P, the probability that p is maximal in I equals the probability that p is
minimal not in I. In this paper, we prove a formula for the expected jaggedness
of an order ideal of P under any toggle-symmetric probability distribution when
P is the poset of boxes in a skew Young diagram. Our result extends the main
combinatorial theorem of Chan-L\'opez-Pflueger-Teixidor, who used an expected
jaggedness computation as a key ingredient to prove an algebro-geometric
formula; and it has applications to homomesies, in the sense of Propp-Roby, of
the antichain cardinality statistic for order ideals in partially ordered sets.
