Directional Hypotheses - Free download as ..
What are examples of directional hypothesis ..
If the conclusion were to support the claim that the antibiotic prolonged group A life spans, then the researchers should use a directional alternate hypothesis, such as Ha: XbarA > XbarB. Here group A's life span is hypothesized to be greater (longer) than group B's (the control group). In this case, an alpha level of 0.05 implies that all 0.05 would have to appear in the right or high tail of the curve, which then is a one-tailed or directional test, as shown in Figure 8-3. This figure shows that the critical t-value will actually be smaller for the one-tail test, that is, +1.65 instead of 1.96 or 2.00 from the two-tail test. This happens because 95% of the area under the curve begins to accumulate from the left-most side of the curve (including that tail) and includes less of the right side of the curve. The result is that tcalc can be smaller (1.65 instead of 1.96) and still cause Ho to be rejected.
Directional and nondirectional alternative hypotheses
Imagine the shrieks that would ensue if judges arrogated to themselvesall of this authority [ANONYMOUS LISTSERVE COMMENT]:"...the hypothesis testing approach focuses the subsequent questions,quite possibly leading to confirmatory bias, and then is disavowed as "evidence."Rogers has advocated that the examiner obtain all the relevant data, withoutprior hypotheses, to avoid premature channeling of the investigation."(Doctorate-level MHP, February 18, 2006).