  When a planner must decide whether it has enough evidence to make a decision
based on probability, it faces the sample size problem. Current planners using
probabilities need not deal with this problem because they do not generate
their probabilities from observations. This paper presents an event based
language in which the planner's probabilities are calculated from the binomial
random variable generated by the observed ratio of one type of event to
another. Such probabilities are subject to error, so the planner must
introspect about their validity. Inferences about the probability of these
events can be made using statistics. Inferences about the validity of the
approximations can be made using interval estimation. Interval estimation
allows the planner to avoid making choices that are only weakly supported by
the planner's evidence.
