  I study a model of costly Bayesian persuasion by a privately and partially
informed sender who conducts a public experiment. The cost of running an
experiment is the expected reduction of a weighted log-likelihood ratio
function of the sender's belief. This is microfounded by a Wald sequential
sampling problem where good news and bad news cost differently. I focus on
equilibria that satisfy the D1 criterion. The equilibrium outcome depends
crucially on the relative costs of drawing good and bad news in the experiment.
If bad news is costlier, there exists a unique separating equilibrium, and the
receiver unambiguously benefits from the sender's private information. If good
news is costlier, the single-crossing property fails. There may exist pooling
and partial pooling equilibria, and in some equilibria, the receiver suffers
from sender private information.
