Creators and designers of research studies must take many factors into account to produce the most accurate study, depending on the type of study and results produced. Validity of a research study is based on its questions and how accurately the study can answer those questions. You can use several control measures to enrich your data and help increase the validity of your study.
Create a control group at the same time you create your study group. When studying the effects of exposure to a variable on your subjects, compare these subjects to subjects that have not been exposed to the variable. Creating a control group will give you a basis on which to draw comparisons.
Account for as many external factors as possible. The more easily you can dismiss factors other than the variable that may have had an external influence on your subjects, the more strongly you will be able to validate your data.
Monitor your study population statistics closely. Over the course of a study, you may lose some of your subjects. If you are dealing with people, some may choose to stop participating, or external factors in their lives may influence your research. Keep these in mind when compiling data. You can help to reduce the problem of subjects leaving your study by offering participation incentives.
Try to prove the opposite of your hypothesis. When creating a research design it is important to not only examine the facts that support your hypothesis, but also look at the factors that do not. See if you can prove your hypothesis wrong. If you can, you can rethink the study parameters; if you cannot, you have continued to strengthen the validity of your study.