Tyler Lizenby/CNET

The Amazon Echo might sell better than its biggest competitor -- the Google Home. But for the second year in a row, a study found that Google's digital assistant is smarter than Amazon's assistant, Alexa. Alexa is catching up, though, as it was far and away the most improved from 2017 to 2018.

Smart speakers use digital assistants to answer your questions and respond to a variety of voice commands. Digital marketing company Stone Temple released the results of its 2018 smart speaker quiz earlier this week. It did a similar test last year in which it asked digital assistants roughly 5,000 questions to see which assistants answer the most correctly.

The company asked the same set of questions to Amazon's Alexa, Apple's Siri, Microsoft's Cortana and Google's Assistant. For the first time this year, Stone Temple asked the questions separately to Google Assistant on the company's Home smart speaker, and an Assistant-equipped phone.

Stone Temple

The study found that Google Assistant attempts the most responses, and gets the most attempted responses correct. Strangely, Assistant performed even better on a phone than on a smart speaker. Surprisingly, Microsoft's Cortana took second place, with Alexa trailing both and Siri lagging far behind the rest.

Alexa doubled the number of questions it was able to answer from 2017 and Microsoft's assistant improved as well, with Google holding relatively steady at the top while its competition catches up.

Stone Temple

Of attempted responses, all smart speakers got over 80 percent of their responses correct. The study goes on to note that most incorrect responses aren't outright wrong, just incomplete. You can see the rest of the results from the study here.

Of course, we can help you pick out the best smart speaker: Here's CNET's breakdown of the battle of digital assistants and a quiz to see which one would best fit your life.

Amazon, Apple and Google did not respond to CNET's request for comment.

A Microsoft spokesperson issued the following statement to CNET over email: "We are proud of our continued work on Cortana and we're excited for what the future holds for continued growth, functionality, and availability across devices and platforms."