CHAPTER 2

LECTURE EXTENSION

Meta-Analysis: Combining the Results of Many Studies
The text indicates that the concept of validity can be applied broadly to the overall accuracy of research findings and conclusions. Consider extending this idea by presenting a brief overview of meta-analysis, a systematic, quantitative method of summarizing the results of many studies that address the same research question.

Meta-analysis helps researchers avoid accepting the conclusions of only one or a few possibly biased investigations. Using special statistical procedures, researchers combine the results of primary investigations that make up the literature on a given topic. These procedures enable them to determine (1) whether the set of results could have arisen by chance; (2) the strength of the effect reported; and (3) the stability of the results. Stability is generally assessed by estimating the number of unpublished studies reporting no difference that would be necessary to wash out the combined results of studies in the review.

The findings of meta-analyses, however, are only as good as the studies that contribute to them. Consequently, researchers engaged in meta-analysis often evaluate the evidence in qualitative as well as quantitative ways, noting characteristics of samples, methods of measuring independent and dependent variables, and other potential threats to the validity of each investigation.

LEARNING ACTIVITY

Designing an Experiment
Pose the following questions to students either as a take-home assignment or in-class discussion:
A researcher is interested is determining whether infant day care leads to (i.e., a cause-and-effect relationships) an insecure attachment bond between children and their mothers during the first year of life as well as into the preschool years. Design a study to examine this question and discuss the type of method and research design you would choose. Would there be any special ethical considerations with this type of study?

An investigator is interested in determining whether sociability in children is related to school achievement and whether this relationship varies for children in preschool, grade school, and middle school. Design a study to examine this question and discuss the type of method and research design you would choose. Would there be any special ethical considerations with this type of study?