1. Introduction to Hypothesis Test – Part 2

2. Directional vs. Non-directional Hypotheses
Directional hypothesis test
the statistical hypotheses specify either an increase or a decrease in the population mean score. (critical region is located in one tail)
Non-Directional hypothesis test
No direction is specified

3. Directional vs. Non-directional Hypotheses
Changes with directional tests
When should directional vs non-directional tests be used

4. Example 1 - revisited
One-tailed test: determine critical regions (=.05)
=26; =4; n=16; m=1; M =30

5. Type I and II errors
The researcher concludes that a treatment has an effect when in fact it does not have an effect.
Risk of a Type I error is small and is under the control of the researcher.
What are the implications of making a Type I error?

6. Type I and II errors
A treatment effect really does exist, but the data was such that the hypothesis failed to detect it.
The p (type II error) depends on a number of factors:
size of the effect
sample size
variability

7. Assumptions
Random sampling – samples should be representative of the population
Independent observations
The value of σ is unchanged by the treatment
Normal sampling distribution