  We describe likelihood-based statistical tests for use in high energy physics
for the discovery of new phenomena and for construction of confidence intervals
on model parameters. We focus on the properties of the test procedures that
allow one to account for systematic uncertainties. Explicit formulae for the
asymptotic distributions of test statistics are derived using results of Wilks
and Wald. We motivate and justify the use of a representative data set, called
the "Asimov data set", which provides a simple method to obtain the median
experimental sensitivity of a search or measurement as well as fluctuations
about this expectation.
