Ultimately, you can only gauge effectiveness when you know what your objectives are.
In evaluation terms, I would use three classes of metrics, but of different kinds.
Ultimately, the only true evaluative measures are financial. Marketing is a business function, pure and simple, and so it needs to generate profit [obviously different with non-profit comms]
However, since immediate sales response is unlikely to show a return on marketing investment, we look at intermediate measures.
These are NOT evaluative - they are diagnostic - they help unpack the intermediate effects of communication and help to give an indication of future profits as well as providing useful inputs to strategy.
Of these I use two classes - cognitive and behavioural.
What people think - unreliable but the core metrics of advertising - awareness, recall etc - tapped via survey.
What people do - more reliable - footfall, phone calls, and EVERYTHING we do online.
The key thing is to use a basket of all 3, in line with objectives. But don't forget, a shift in awareness is NOT an objective unless it leads to profit.
Philosophically, the respective questions: Is the creative solution Relevant, Distinctive and True to the brand and the marketing challenge it intends to impact? Can the idea be delivered in a context that will yield the desired level of perceptual, behavioral or experiential change. If the above theoretical issues are judgementally sound, the range of pre and post qual and quant "metrics" implied are dependent upon the proposed ideas.
I'm sure this just another way of saying 'what are your objectives', but how are you defining engagement? Or, can you define engagement to one thing [the objective] and then measure that.
I've started to notice that defining engagement is getting more and more clouded and that there are differences between different types of engagement. For example media engagement, consumer engagement, brand engagement, WOM engagement all have their own twists.
Media engagement focuses on how we [consumer] engage with the medium.
Content engagement is how we engage with the content within a medium.
Both of those can have very different types of measurement.
Switching gears, there has been studies lately that have shown that engagement = market share. But the problem in the studies is chicken/egg. Does high market share inherently drive brand engagement (regardless of engagement measure) or does have consumer engage with a brand drive purchase market share? I don't have the link, but the original study working on this is from the Athena; Integration; Advertising and Marketing Communications Roundtable. I think I have the email from the guy who presented it...maybe...
Having said all that, I have been leaning towards defining brand engaging to number of recommendations. It gets at the nature of WOM and what people think of a brand.
Hope this drives some thoughts...say hi to Lori and the team