## NCA parameters

What is the ceiling zone?

The ceiling zone (C) is the “empty” space above the ceiling. Because a small proportion of observations (e.g., 5%) may be in the “empty” space, the ceiling zone may be “virtually empty”.

What is accuracy?

Accuracy is the percentage of observations that are on or below the ceiling.

What is the scope?

The scope (S) is the total potential space with observations given the minimum and maximum values of the condition and outcome.

What is the theoretical scope?

The theoretical scope is the scope with theoretical minimum and maximum values of the condition and the outcome.

What is the empirical scope?

The empirical scope is the scope with observed minimum and maximum values of the condition and the outcome.

What is the effect size?

The necessary condition effect size (d) is the proportion of the scope above the ceiling: d = C/S. It ranges from 0 to 1 (0 ≤ d ≤ 1). The effect size indicates to what extent the condition is necessary for the outcome.  In other words: to what extent the condition constrains the outcome, and the outcome is constrained by the condition.

What is a general benchmark for the effect size?

“An effect size can be valued as important or not, depending on the context. A given effect size can be small in one context and large in another. General qualifications for the size of an effect as ‘small,’ ‘medium,’ or ‘large’ are therefore disputable. If, nevertheless, a researcher wishes to have a general benchmark for necessary condition effect size, I would offer 0 < d < 0.1 as a ‘small effect,’ 0.1 ≤ d < 0.3 as a ‘medium effect,’ 0.3 ≤ d < 0.5 as a ‘large effect,’ and d ≥ 0.5 as a ‘very large effect’.”(Dul,  2016, p.30).

What is condition inefficiency?

Condition inefficiency is the percentage of the range of the condition where the condition is not necessary for the outcome. In other words: where the condition does not constrain the outcome.

What is outcome inefficiency?

Outcome inefficiency is the percentage of the range of the outcome where the condition is not necessary for the outcome. In other words: where the outcome is not constrained by the condition.

What is the bottleneck table?

The bottleneck table is a tabular representation of the ceiling. It indicates the required necessary level of the condition(s) for a given level of the outcome. The bottleneck table is particularly useful for interpreting multivariate necessary conditions, and identifying necessary AND configurations.