Make all training sessions mandatory.
Yes, this will improve the measurement, or metric, by ensuring that all the employees are at least present at the training, but is it the final answer? Read on!
Have employees fill out a survey about the training to indicate how they liked it.
This is not a very helpful metric, unfortunately, other than it may indicate whether the diversity training needs to be revised. In terms of actually helping measure cultural awareness, a different type of survey might be useful, such as a post-training survey that asks attendees what they learned and measuring answers against a pre-test administered prior to the training about cultural understandings the employees hold.
Test employees’ cultural awareness.
This is an interesting metric! You could lead the employees through a diversity simulation game such as BaFa BaFa (url: http://www.simulationtrainingsystems.com/corporate/products/bafa-bafa/).