We want to follow the lead and advice of a legitimate authority. (for example, take a look at the Milgram Experiment)
We all look for guidance and direction to some extend. Especially when something is new and users feel a little uncertain about what to do or what to choose. An authority figure or brand can guide them through you webshop to reassure them and give them direction on what the right choices are. Consider letting famous/ well known people from within your community or from TV to promote your products or your brand. Repeat Cashmere has a Magento based e-commerce webshop and does a perfect job on 'exploiting' this theory. They have top model Doutzen Kroes promoting their product on their webshop. Well done!
Recently I've seen some (often absolute) statements going around, generally in the line of "open source commerce platforms are a terrible idea". Now of course different solutions always have different pros and cons.
A hierarchy of evidence (or levels of evidence) is a heuristic used to rank the relative strength of results obtained from scientific research. I've created a version of this chart/pyramid applied to CRO which you can see below. It contains the options we have as optimizers and tools and methods we often use to gather data.