Sunday, May 24, 2015

user behavior - How to make a progress-speed bar more understandable?


I've just installed Windows 8 and noticed the brand new File copying dialog. When expanded, it shows the progress and the current transfer speed in one graph. However, the graph confuses me greatly. The faster it copies, the quicker progress increases (left-to-right) and the higher the graph (bottom-to-top). I think this makes the speed graph non-linear, and I have trouble reading the graph. This makes the graph no more than a toy.


A Dutch progress/speed bar in the Windows 8 copy dialog


It's in Dutch but I think the gist is clear.


I assume Microsoft's design team have discussed all pros and cons of this graph, so there must be some merit to this design. I would like to write a custom control for my own application that also shows progress and speed in one bar, but I don't think this is the way to go. How to make the speed part of the bar more understandable and useful? What are the alternatives?




To illustrate the problem I have with it:


Half the time at full speed, half the time at half the speed.



This graph indicates that for half of the total transfer time, the file was copied at half the speed (e.g. 30 seconds of half speed if the total copying took one minute). That would be useful information but is not clear to me from the graph.



Answer



You can overlay your progress bar with a transfer rate graph pegged to 100% width. The result is a constantly updating histogram that remains linear throughout the operation. This gives you a simple way to display both progress and transfer rate on the horizontal axis. An example:


enter image description here


This is a rough visual example; to make it more readable you'd want to properly label things to ensure the progress bar and the histogram are district.


If your users care about watching throughput over time -- perhaps for debugging or instrumentation purposes -- this layered approach provides an easy way to monitor it during the operation. If users aren't expecting this data or this type of design, they might just find it distracting.


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