From a Dalitz plot analysis of B→Kπ+ψ′ decays, we find a signal for Z(4430)+→π+ψ′ with a mass M=(4443-12-13+15+19)MeV/ c2, width Γ=(107-43-56+86+74)MeV, product branching fraction B(B̄0→K-Z(4430)+)×B(Z(4430)+→π+ψ′)=(3.2-0.9-1. 6+1.8+5.3)×10-5, and significance of 6.4σ that agrees with previous Belle measurements based on the same data sample. In addition, we determine the branching fraction B(B0→K*(892)0ψ′)=(5.52-0.32-0.58+0.35+0. 53)×10-4 and the fraction of K*(892)0 mesons that are longitudinally polarized fL=(44.8-2.7-5.3+4.0+4.0)%. These results are obtained from a 605fb-1 data sample that contains 657×106 BB̄ pairs collected near the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. © 2009 The American Physical Society.