HELP:How do we evaluate the effectiveness of *insert element/principle*

[playsimme]

K so PLEASE HELP! I know there's someone who's a guru at this! How do we evaluate CORRECTLY the effectiveness of say, color/line or a random element/material? I need to know because sometimes I blabber on for 4 marks but only score minimal points
Do we need to refer to something like the target audience? Is there a formula? Please help! Share your secrets! It's the ultimate bullshitting questions but I need a formula so I bullshit correctly

[spikey]

Hmmm well I find colour and letterform easy to talk about in terms of effectiveness to a target audience.
Bright, vibrant primary colours = kids
Duller neutral colours = older adults

And then for letterform sans serif = modern and fun
Serif = traditional, typically adults

Not sure if this answers your question enough but that seems to be my formula for those two

[whitesebastian]

I suppose an interesting way for you to think about it would be see who it's directed at, put yourself in the mind of the person, and think about how it would appeal to you.
If there's a kid's flyer for some playpark or something, imagine you're a child and think, why would I like that type, why would I like those colours, why would etc. etc.
it should hopefully come to you like that, I'd say.