Life sciences

Typical cases are cases that exemplify a stable cross-case relationship. These cases are representative of the larger population of cases, and the purpose of the study is to look within the case rather than compare it with other cases.

Diverse cases are cases that have variation on the relevant X and Y variables. Due to the range of variation on the relevant variables, these cases are representative of the full population of cases.

Extreme cases are cases that have an extreme value on the X or Y variable relative to other cases.

Deviant cases are cases that defy existing theories and common sense. They not only have extreme values on X or Y (like extreme cases), but defy existing knowledge about causal relations.

Influential cases are cases that are central to a model or theory (for example, Nazi Germany in theories of fascism and the far-right).

Most similar cases are cases that are similar on all the independent variables, except the one of interest to the researcher.

Most different cases are cases that are different on all the independent variables, except the one of interest to the researcher.

Arend Lijphart, and Harry Eckstein identified five types of case study research designs (depending on the research objectives), Alexander George and Andrew Bennett added a sixth category:^[22]

1. 
   In atheoretical (or configurative idiographic) case studies the goal is to describe a case very well, but not to contribute to a theory.
   
2. 
   In interpretative (or disciplined configurative) case studies the goal is to use established theories to explain a specific case.
   
3. 
   In hypothesis-generating (or heuristic) case studies the goal is to inductively identify new variables, hypotheses, causal mechanisms and causal paths.
   
4. 
   In theory testing case studies the goal is to assess the validity and scope conditions of existing theories.
   
5. 
   In plausibility probes the goal is to assess the plausibility of new hypotheses and theories.
   
6. 
   In building block studies of types or subtypes the goal is to identify common patterns across cases.
   

In terms of case selection, Gary King, Robert Keohane, and Sidney Verba warn against "selecting on the dependent variable". For example, researchers cannot make valid causal inferences about war outbreak by only looking at instances where war did happen (the researcher should also look at cases where war did not happen). There is no methodological problem in selecting on the explanatory variable, however. They do warn about multicollinearity (choosing two or more explanatory variables that perfectly correlate with each other).^[23] While random selection of cases is a valid case selection strategy in large-N research, there is a consensus among scholars that it risks generating serious biases in small-N research.^[24][23][21]
In public-relations research, three types of case studies are used:^[25]

1. 
   Linear,
   
2. 
   Process-oriented,
   
3. 
   Grounded.
   

Under the more generalized category of case study exist several subdivisions, each of which is custom selected for use depending upon the goals of the investigator. These types of case study include the following:

• 
  Illustrative case studies: These are primarily descriptive studies. They typically utilize one or two instances of an event to show the existing situation. Illustrative case studies serve primarily to make the unfamiliar familiar and to give readers a common language about the topic in question.
  
• 
  Exploratory (or pilot) case studies: These are condensed case studies performed before implementing a large scale investigation. Their basic function is to help identify questions and select types of measurement prior to the main investigation. The primary pitfall of this type of study is that initial findings may seem convincing enough to be released prematurely as conclusions.
  
• 
  Cumulative case studies: These serve to aggregate information from several sites collected at different times. The idea behind these studies is that the collection of past studies will allow for greater generalization without additional cost or time being expended on new, possibly repetitive studies.
  
• 
  Critical instance case studies: These examine one or more sites either for the purpose of examining a situation of unique interest with little to no interest in generalization, or to call into question a highly generalized or universal assertion. This method is useful for answering cause and effect questions.
  

Marketing analysis[edit]
Some cases study marketing analysis to ensure a full understanding of the effects on an organization. In a case where the market of any organization is in jeopardy, the agency will seek answers and solutions. In order to fulfill this need, the organization must gather pertinent information. Case studies can be used to establish where the problem originates by utilizing several research methods. ^[26] Research methods should be chosen appropriately to conduct a thorough investigation. The primary methods used include: interviews, surveys, focus groups, observations and in some cases, field trials.^[27] The methods chosen rely heavily on the amount of capital the organization is able to spend and the kind of data that is required by the group.