Is there a reason to use a discrete plot (like the number of stars) for continuous sizes (like a progress bar)? This assumes that we do not want to display an exact number. (Yes, I understand that values in computers are not "really" continuous, but for the purposes of this question, we'll say they're close enough.)
This question arises from my car and its stress-inducing gas gauge. This is what it looks like when it's full:
The gas gauge consists of 6 stacked bars, all of which light up when the gas tank is full. This is what it looks like when it is almost empty:
It's getting worse here. This bottom bar will flash approximately once every second any Time is the meter on a bar. In other words, the last fuel gauge flashes for about 17% of a full tank. Since I drive mostly full to empty, the car seems to tell me that 17% of the time I drive it, has no more gas (and distracts me with a flashing light)
Now some short calculations to show how stressful this is:
The tank size is just over 6 gallons. The fuel efficiency is, however, on average ~ 45mpg (why I like the car). This means that when the tank is full, I have a range of about 270 miles.
The last bar on the gas gauge therefore corresponds to a range of about 75 km. To put this into perspective: With the shuttle service and everything I drive about 32 km per day. This means that I can actually drive for 2 full days while the car screams that it is about to run dry. When I get in my car in the morning and the bar flashes I can play the funny game "Can I actually make it work today?" Play.
Apart from that, it seems to be the obvious solution to have a tighter continuous measurement. Even if there were only 10 measures instead of six, the user can better assess the actual value.
Is there a UX reason, or is it just a bad design?