1. Comparative Method I
Comparative methods deal primarily with finding and/or eliminating necessary and/or sufficient conditions that produce a given outcome.
Qualitative researchers tend to look at cases as wholes, and they compare whole cases with each other.
While cases may be analyzed in terms of variables, cases are viewed as configurations - as combinations of characteristics. Comparison in the qualitative tradition thus involves comparing configurations.  
At a very general level, comparativists are interested in identifying the similarities and differences among macrosocial units.
The basic idea of the logic of elimination in comparative methodology is based on John Stuart Mill’s methods of agreement and difference.

2. Comparative Method II John Stuart Mill – System of Logic 1848
Method of Agreement
“If two or more instances of the phenomenon under investigation have only one circumstance in common, the circumstance in which alone all the instances agree, is the cause (or effect) of the given phenomenon.”
Find cases in which the effect has occurred
Determine if there is only one thing that they all share
If there is, then that thing is likely the cause

3. Comparative Method III
John Stuart Mill – System of Logic 1848
Method of Difference
“If an instance in which the phenomena under investigation occurs and an instance in which it does not occur, have every circumstance in common save one, that one occurring only in the former, the circumstance in which alone the two instances differ, is the effect, or the cause, or an indispensable part of the cause, of the phenomenon.”
Find two things that differ in that one has the effect and the other does not
If there is only one factor on which they differ, that is the likely cause

4. Joint Method of Agreement and Difference
Comparative Method IV
Joint Method of Agreement and Difference
- Find something in common amongst all cases where the effect appears
- Find matches for all these cases except that they lack the effect and the common ingredient
Example:
Five factory workers are found to be inefficient relative to others who are doing the same work.
The efficient workers and the inefficient workers were found to be similar in all relevant ways except one: the inefficient workers were not part of a profit sharing plan.
Conclusion: profit sharing causes efficiency.

5. Method of Concomitant Variation
Comparative Method V
Method of Residues
“Subduct from any phenomenon such part as is known by previous inductions to be the effect of certain antecedents, and the residue of the phenomenon is the effect of the remaining antecedents.”
Method of Concomitant Variation
“Whatever phenomenon varies in any manner whenever another phenomenon varies in some particular manner is either a cause or an effect of that phenomenon or is connected with it through some fact of causation.”

6. Comparative Method VI

7. QCA Concepts I QCA: what is the purpose?
Necessity/ Sufficiency causal inference.
Conditions are “public” as they appear clearly and are justified.
The path is the essence.
It aims at a causal interpretation.
QCA makes use of so-called truth tables.
QCA approaches make use of the principles of logical minimization, a process by which the empirical information is expressed in a more parsimonious yet logically equivalent manner by looking for commonalities and differences among cases that share the same outcome. 

8. QCA Concepts II The QCA is useful technique when:
working with a small number of cases;
when theory implies a combinatorial logic between conditions;
when it is possible to find different causal paths to the same outcome (equifinality);
when is possible to find necessary and sufficient conditions to specific results.
The analytic strategy is to identify causal conditions shared by cases with the same outcome.

9. QCA Concepts III
QCA methodology is useful in answering two basic questions.
First, what are the specific causes or combinations of causes that constitute a necessary condition for the outcome? These combinations must be always present for the outcome.
Second, what are the specific causes or combinations of causes that constitute sufficient conditions for the outcome?
These combinations represent one of several possible paths, which always or almost always, lead to the result. Therefore, a common finding is that a given outcome may result from several different combinations of conditions.
These combinations are generally understood as alternative paths or recipes for the result, and they are treated as logically equivalent (i.e., as substitutable) .

10. QCA Concepts IV
Two measures - consistency and coverage - are used to evaluate whether the data produces potential answers to these questions.
When one searches for necessary conditions, consistency assesses the degree to which instances of an outcome also display the causal condition thought to be necessary.
When one looks for sufficient conditions, coverage assesses the degree to which the cases sharing a given causal factor or combination of causal factors all display the outcome in question.
In this context, consistency assesses the degree to which instances of an outcome display the causal condition thought to be necessary, whereas coverage tell us the degree to which instances of the causal combination are paired with instances of the outcome.

11. QCA Concepts V QCA: basic principles
Cases are represented by conditions (independent variables) and an outcome (dependent variable)
The presence of conditions is noted for every case

12. QCA Concepts VI QCA: how it works? Meticulous case selection
The choice of the variables and the cases must be theoretically informed
Irrelevant cases should be excluded from the data set because their inclusion does not benefit hypothesis testing and, indeed, may hinder it.
As for case studies: (1) a representative sample and (2) useful variation on the dimensions of theoretical interest.
The subset of case comparison > the outcome

13. QCA Concepts VII QCA: how it works? Meticulous variable selection
Based on the principle of “configurations”
Many times one “condition” is not enough as to evidence a necessary/ sufficient causation
Identify which variables are relevant to the question at hand, explain how these variables are related to one another, and, specify the contexts under which they operate
If a given theory has multiple necessary or sufficient conditions, how can we determine if one is more important than another? > relevance of the variable

14. QCA Concepts VIII
QCA is grounded in the analysis of set relations, not correlations.
Because social theory is largely verbal and verbal formulations are largely set theoretic in nature, QCA provides a closer link to theory than is possible using conventional quantitative methods.
Note also that important causal relations, necessity and sufficiency, are indicated when certain set relations exist: With necessity, the outcome is a subset of the causal condition; with sufficiency, the causal condition is a subset of the outcome.

15. QCA Concepts IX Necessary Conditions
X is a necessary condition for Y if Y is a subset of X.

16. Sufficient conditions
QCA Concepts X
Sufficient conditions
X is sufficient for producing Y, but not necessary: there are parts of Y that do not include X. Meanwhile each time you have X you have Y.

17. QCA Concepts XI
The knowledge of the causes for an outcome does not imply a determinate path for a contrary outcome
Therefore, in QCA we must always develop two analysis: one for the outcome 1, one for the contrary (outcome = 0)
Example: a father wonders why some children have been invited by his son to a birthday party
Possible conditions for an invitation (outcome)
Girl: yes (g=1), no (g=0)
Age (4 years or older (a=1); else (0))
Same kindergarden (yes (k=1); no (k=0))

18. QCA Concepts XII