Answer to "How to select a range of selection methods?"
At this point, most medical schools use a combination of tools that assess knowledge and/or cognitive ability (such as prior attainment or GPA), and non-cognitive factors (personal attributes):
Lievens F. Adjusting medical school admission: Assessing interpersonal skills using situational judgement tests. Medical Education 2013: 47(2): 182-189.
It is useful to know that tools measuring cognitive skills (e.g., prior attainment or GPA) seem better at predicting academically-loaded assessments in the earlier years of medical school, whereas assessments of personal attributes (e.g. MMIs, SJTs) seem to be better at predicting more clinically-oriented performance in the later years of medical education (see Patterson et. al., above).
Why use two tools which measure similar things (e.g., prior attainment and a knowledge-based entry test, or an MMI and an SJT) when one would do? See:
Husbands A, Rodgerson MJ, Dowell J, Patterson F. Evaluating the validity of an integrity-based situational judgement test for medical school admissions. BMC Medical Education. 2015; 15: 144.
Roberts C, Clark T, Burgess A, Frommer M, Grant M, Mossman K. The validity of a behavioural multiple-mini-interview within an assessment centre for selection into specialty training. BMC Medical Education. 2014; 14: 169. (This paper has a postgraduate medical training focus, but compares an MMI and SJT so may have transferable messages to medical school contexts).
Every country has own, explicit or implicit inequalities in education. Given this, you may also wish to include an aptitude test in your selection portfolio, to assess potential, rather than depending on prior attainment if prior attainment is associated with social factors beyond the control of the individual (see later for further discussion).
Medical schools also need to be practical in their selection of selection methods – what is feasible, what do you have the resource and expertise to roll out locally? There is a balance to achieve between the “best” tools, or combination of tools, and what is practical for your context.