Health Promotion Evaluation Designs, Assessment Example

Week 8: Study Design and Internal Validity

1a. X_T O₂

1b. The internal validity issue with a single group post-test only is that it is a one-time survey following the intervention. Therefore, it cannot identify the changes which have have resulted between the baseline and the intervention. In addition, it does not contrast between groups. The test is only useful at providing a single snapshot of a group following an intervention which can be contrasted with standardized materials such as national data.

2a. Pre-test post-test control group design

2b. The threats to internal validity may result from only one group receiving the initial treatment while both groups are post-tested (no placebo). In addition, the design assumes the groups are not random but equivalent. This may produce type 2 beta error.

3a. O1 x O2

O3 ? O4

3b. The key threats to internal validity for this design are additive and interactive effects along with differential attrition and selection. This stems from a lack of random group placement which makes it suspect to decide that the post-test difference is a result of the intervention.

4a. One group pre-test post-test

4b. A number of issues affect the internal validity of this intervention. First, a number of things might happen between the two occurrences. Second, the effect of testing at the first occurrence may have influence the subject’s ad well as the measurer’s performance at the second occurrence.

5a. O1 x O2

O3 x O4

O5 x O6

O7

5b. This test is superior to the others, however similar to the one group pre-test post-test one must be concerned with history and measurement as confounding variables.