  We consider interval estimation of the difference between two binomial
proportions. Several methods of constructing such an interval are known.
Unfortunately those confidence intervals have poor coverage probability: it is
significantly smaller than the nominal confidence level. In this paper a new
confidence interval is proposed. The construction needs only information on
sample sizes and sample difference between proportions. The coverage
probability of the proposed confidence interval is at least the nominal
confidence level. The new confidence interval is illustrated by a medical
example.
