The average attention span of a visitor to your landing page is less than 8 seconds. If there is an explainer video on your page, it will not only grab your viewers’ attention but keep it, as the average sticking time on a web page with video is 2 minutes. If your video is engaging and entertaining, your viewer will see it through to the end, by which time – with an awesome explainer video – you will have increased your likelihood of a sale by 85%, introduced your brand and created an emotional bond with your customer.
I would qualify that statement with: "a GOOD explainer video..."
That means one that's not only technically professional in the audio and lighting/photography, but also immediately begins to answer the most important questions a viewer would have, while enticing them to explore more deeply and stick around the site.
Some "explainer" videos I've seen online have an identity problem, trying to decide if they are promos or instructionals; they either don't have enough "meat", i.e. actionable information in them, or they assume too much advance knowledge by the viewer, delving right into obscure operational lectures or how-to's without a proper introduction first.
What I tell any client wanting to do an instructional is to first write a 5-question viewer quiz about the key points. If a viewer with no other information but the instructional can watch the video and then answer at least three of the quiz questions correctly, you're on the right track. Fewer than three right answers means going back to re-tool the program.