Mokken scale

[1] Mokken Scales have been used in psychology,[2] education,[3][4] political science,[1][5] public opinion,[6] medicine[7] and nursing.

Both Guttman and Mokken scaling can be used to assess whether a number of items measure the same underlying concept.

However, Mokken scaling is described as 'non-parametric' because it makes no assumptions about the precise shape of the item response function, only that it is monotone and non-decreasing.

[5] Mokken scales can come in two forms: first as the Double Monotonicity model, where the items can differ in their difficulty.

[11] There has been some confusion in Mokken scaling between the concepts of Double Monotonicity model and invariant item ordering.

[3] Using real data from the Warwick Edinburgh Mental Well Being Scale (WEMWBS)[15] suggests that the required sample size depends on the Mokken scaling parameters of interest as they do not all respond in the same way to varying sample size.

Also within the R (programming language), unusual response patterns in Mokken Scales can be checked using the package PerFit.