We need to be assured we're making te right decision.
What can you do to provide certainty in your webshop? Let people know their making the right decision by taking away doubt and ambiguity which might cause inaction. Provide clear benefits of your products and provide social proof of other customers who're happy they've made the decision (of buying your products).
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.