 The criterion for rejecting formula_13 thus requires that the ratio formula_14 will be smaller than formula_15.This can be interpreted intuitively as saying that formula_8 is excluded because it is formula_15 less likely to observe such an extreme outcome as "X" when formula_8 is true than it is when the alternative formula_19 is true.The calculation of the upper limit is usually done by constructing a test statistic formula_20 and finding the value of formula_21 for which

where formula_23 is the observed outcome of the experiment.