The baseline assessment of spatial ability is being done via 2 tests: The Vandenburg and Kuse Mental Rotation Test and the CEEB Mental Cutting Test. Both are reliable, valid and well suited to the study. Example problems from both tests are here:
I got a couple of large groups of participants to do these tests immediately after consent to participate. The rationale for asking them to do this was as follows:
- They need to be timed and invigilated.
- I need the data to add to the minimisation algorithm before allocation.
- It saves a lot of time on the main data collection days that they attend.
- Do these tests after other aspects of data collection. This would mean using simple randomisation instead of minimisation (actually someone from the research centre wondered why I wasn't doing this anyway, suggesting that it would be perfectly acceptable) but I could still end up with attrition later in the study if they give up on the SA tests later rather than sooner?
- Explain to other prospective participants that the SA tests are quite tough and that low scores are not something to worry about. Essentially try to encourage them to give them a go and continue with participation.
- Accept that attrition will occur as a result of this, accept it and discuss the limitations in the thesis.