Читать книгу Health Psychology - Michael Murray - Страница 114

Cross-sectional designs obtain responses from respondents on one occasion only. With appropriate randomized sampling methods, the sample can be assumed to be a representative cross-section of the population under study and it is possible to make comparisons between sub-groups (e.g., males versus females, older versus younger people, etc.). However, cause and effect can never be inferred between one variable and another and it is impossible to say whether the observed associations are caused by a third background variable not measured in the study.

Cross-sectional designs are popular because they are relatively inexpensive in time and resources. However, there are problems of interpretation; not only can we say nothing about causality, but generalizability is also an issue whenever there is doubt about the randomness or representativeness of the samples. Many studies are done with students as participants and we can never be sure that the use of a non-random, non-representative sample of students is methodologically rigorous. The ecological validity of the findings is strongly contentious in the sense that they are unlikely to be replicated in a random sample from the general population. Any study with a non-random student sample should be repeated with a representative sample from a known population. Cross-sectional designs are also unsuited to studies of behaviour change and provide weak evidence in the testing of theories.