Do you have any proof that they help?
You can choose to pay for study materials rather than just reading MMI questions and then using common sense if you so desire. Do some practice MMI questions then take the free practice CASper and if you find it difficult in a way that you can study for, pay for some study materials.
It is all stuff that you ~should~ be able to answer on your own. For example, if someone with tattoos comes into the clinic, how do you treat them differently than an non-tattooed middle-aged patient? Do you add additional questions about drugs to the tattooed patient?.....the answer is obviously that you do nothing differently because that would be discrimination. Pressing the tattooed person on drugs would make them uncomfortable. All doctors should ask a comprehensive set of questions to ALL patients so that they aren't being discriminatory and aren't missing non-stereotypical druggies. (This is a practice mmi scenario)
Now if it's a situation with two sides, you present both sides.
Stuff like that. It's not stuff you need to learn about in a book. It is just common sense.
Yes, CASPer is an SJT and there's lots of research on SJTs and the research shows that especially behavioral SJTs (which CASPer) benefit from advanced preparation. See the following:
Whetzel, D. L., & McDaniel, M. A. (2009). Situational judgment tests: An overview of current research. Human Resource Management Review, 19, 188-202.
Nguyen, N. T., Biderman, M. D., & McDaniel, M. A. (2005). Effects of response instructions on faking a situational judgment test. International Journal of Selection and Assessment, 13, 250-260.
Cullen, M.J., Sackett, P.R., & Lievens, F. (2006). Threats to the operational use of situational judgment tests in the college admission process. International Journal of Selection and Assessment, 14, 142-55.
Ebo K. A Osam (2014) The Adaptation of a Situational Judgement Test to Measure Leadership Knowledge in the Workplace, Western Kentucky University
Honestly, that practice example MMI scenario you gave is a lot easier than the practice CASPer questions I've been doing. My friend said their scenarios on their actual CASPer test last year were A LOT more complicated. There were a few involving sports teams where it was not EASY to make a decision, as well as personal behavioral questions that really threw them off guard. I'm hoping that doesn't happen to me!