This describes the difference

1. Differentiating between
directional and non-directional
hypotheses

2. Non directional – also called two
tailed
• Experimenter predicts that two groups will
be different; but doesn’t say in what
direction
• Ho: μ1 = μ2 (null hypothesis)
• H1: μ1 ≠ μ2 (alternative hypothesis)

3. Directional
• Experimenter predicts that one group will
do better than the other (in this example E
predicts that group 1 will be greater than
group 2)
• Ho: μ1 ≤ μ2 (null hypothesis)
• H1: μ1 > μ2 (alternative hypothesis – this
is the experimenter’s prediction)

4. Directional prediction
• If E predicts that group 1 is less than
group 2 then:
• Ho: μ1 ≥ μ2 (null hypothesis)
• H1: μ1 < μ2 (alternative hypothesis – this
is the experimenter’s prediction)