how do you quantify the success of a design?
short question
if an expert user's time per task is 15 seconds, and im somehow able to lower a first time user's time from 3 minutes to 1 minute and 50 seconds, is that considered a successful design? if not, what number is considered "successful"?
details
im a graphic designer and it's my first time trying out user testing and im feeling a bit overwhelmed 😅
im trying to conduct a very simple user test of an app. im planning on measuring how long it takes for a first time user to complete tasks in an app and comparing their task times to expert users. am also measuring number of errors per task.
i'll be making an app prototype based on what i find and comparing first time users' task times using the old app vs my prototype.
ideally, i'd like their task time using my prototype to be as fast as that of an expert user; but realistically i know i can improve their task times but not get them to expert user level.
for context, the current interface is so unintuitive that someone needs to teach every new user how to navigate the app. the users are delivery drivers and are almost always in a rush and have no time to focus and figure out how to navigate the app.