Strengths and weaknesses of snapshot study?

One problem with a longitudinal study is that a relationship is built with participants, making it difficult for the researcher to remain objective. In a snapshot study, that relationship isn't built, making it easier to remain objective, reducing researcher bias. Researcher bias is an extraneous variable, which can affect the dependent variable, whereas only the independent variable should affect it. This can make it more difficult to establish cause and effect.

In addition, subject attrition isn't as much of an issue in snapshot research (where participants drop out), so therefore the sample is just as large as it was when the study started. Therefore, the sample remains unbiased - as in longitudinal research only a particular type of person would continue in the study - and representative.

However, a snapshot study doesn't show a behaviour developing in the same group like longitudinal research does, therefore, participant variables become an issue. Participant variables are an extraneous variable, which can affect the dependent variable, whereas only the independent variable should affect it. This can make it more difficult to establish cause and effect.