The Null Hypothesis for a Directional H 1 Asserts That

Short Answer

The null hypothesis for a directional H 1 asserts that chance alone is at work or there is a real effect in the direction opposite to that predicted by H 1 . This is a correct statement, and yet we reject or retain this H 0 based on assuming chance alone is at work. What about the possibility of a real effect in the opposite direction?