  This paper reports experimental results comparing a mixed-initiative to a
system-initiative dialog strategy in the context of a personal voice email
agent. To independently test the effects of dialog strategy and user expertise,
users interact with either the system-initiative or the mixed-initiative agent
to perform three successive tasks which are identical for both agents. We
report performance comparisons across agent strategies as well as over tasks.
This evaluation utilizes and tests the PARADISE evaluation framework, and
discusses the performance function derivable from the experimental data.
