One study was an uncontrolled before and after study. Pittet et al.’s (2000) study is a landmark study in HH research. Uncontrolled before and after studies are relatively simple to conduct and superior to observational studies. However, the weak design may make it difficult to attribute observed changes to the intervention and overestimate the effects of interventions (Polit & Beck, 2012).
One study had a pretest–posttest design. Pretest–posttest designs can be used with or without control groups. Limitations include threats to internal validity. A two-group control group pretest-posttest design has strong internal validity, because the pretest ensures the groups are equivalent (Polit & Beck, 2012). This design allows researchers to compare the final posttest results between the two groups, indicating the overall effectiveness of the intervention. The researcher can determine if one, both or neither group changed from pretest to posttest. External validity is reduced due to the reactive or interaction effect of pretesting. Data