Science is all about gaining knowledge, coming up with the best possible explanations of the world around us. So how do we decide which explanation is the best one? How do we make sure our explanations are accurate? How do we determine we actually know something? In science we try to resolve these questions by using a set of principles and procedures called the scientific method. You need to know its historical and philosophical 'origin story' to really understand the scientific method and to fully appreciate how hard it is to apply the scientific method in the social and behavioral sciences!

In the first module we discussed how the scientific method developed, general philosophical approaches and the types of knowledge science aims to find. In this second module we'll make these abstract principles and concepts a little more concrete by discussing the empirical cycle and causality in more detail. We’ll see how, and in what order these concepts are implemented when we conduct a research study. We'll also consider the main criteria for evaluating the methodological quality of a research study: Validity and reliability. The focus will be on internal validity and how internal validity can be threatened.

In the previous module we discussed the empirical cycle, causality and the criteria for methodological quality, focusing on threats to internal validity. In this module we'll consider the most frequently used research designs and we'll see how they address threats to internal validity. We'll look at experimental, quasi-experimental and correlational designs, as well as some other designs you should be familiar with. To understand and appreciate these designs we will discuss some general concepts such as randomization and matching in a little more detail.

Choosing a design is only the first step in the deduction phase (remember the empirical cycle?). The second step is deciding on specific ways to measure the variables of interest and disinterest. This step is extremely important, because even if we are able to perform a true double-blind experiment, if our measurement and manipulation method are of poor quality, then internal validity will still be compromised! In this module we'll look at what measurement is exactly and what the criteria for evaluating measurement are. We will also look more in-depth at self-report measures, including survey, questionnaires and tests. These methods are among the most frequently used measurement instruments in the social and behavioral sciences.