I'm trying to estimate the ROI of a social media campaign but the main issue I'm falling into is linking social media spend to actual company sales. More followers/tweets/likes/fans etc may just mean more followers/tweets/likes/fans and not translate into sales. I have tonnes of data about the campaign itself e.g. spend, followers gained, lost, engagements etc but nothing to really tie it into direct sales for the company.
I could assume an average purchase value but I fear this would just scale things incorrectly e.g. if you were comparing a coca cola can purchase to an expensive perfume purchase the ROI may be the same but the perfume purchase would require much less additional followers (assuming a linear relation between the number of followers and purchases) just because the price is higher.
I'm posting here for a more elegant statistically sound way minimizing assumptions. I'm just predicting past performance so no need for predictions.
My hunch is to analyse and look for 'positive' words in each tweet or something and assume that equal a sale. But not sure that makes sense as would someone tweet/post on FB everytime they buy a coffee?
Any ideas are welcome.