Miller, N. (2013). Measuring up to speech intelligibility. International Journal of Language and Communication Disorders, 48(6), 601-612. doi: 10.1111/1460-6984.12061
Here is what he wrote about the Intelligibility in Context Scale on page 608:
However, there are already examples of attempts at combining the complementary perspectives of signal independent and signal dependent intelligibility in order to gain insights into social interactive implications of different levels of intelligibility... McLeod et al. (2012) employed a set of ‘Intelligibility in Context’ questions alongside intelligibility scores – e.g. Do you understand your child; Do strangers understand your child?, rated on a five point ‘always’ to ‘never’ scale. This provides a method to capture listener and situational variation. It also offers a way of gauging changes in functional success in relation to developments in signal dependent changes. Making such combined judgement has the advantage that it permits one to gain inroads into what counts as a clinically, communicatively, as opposed to merely statistically significant change in intelligibility, either generally, or, more realistically, in relation to given listeners, in given situations.
