Hi,
I'm making a timeline with relatively small bars representing events over time. Right now they are roughly 8px by 200px (the length is variable, but all are 8px high).
Is there a standard reference for what size is standard or minimum for what types of interaction? For example I just want a mouse-over on these bars to highlight them and provide a tooltip, where I imagine if I expected a user to click on these bars, a bit bigger might be more realistic.
Anyone have any insights on this?
It'd probably be pretty hard to find guidelines specific to what you want to do.
There are several things you could do. Wikipedia has a nice article on usability
My main advice would be to think about what your users need, and what they are capable of using/learning. What you could do is make a few different versions where you change a parameter (such as the height of the bars) and get different people to test each one.
Personally, I would be happy to use bars that were 8px high. I would not be so happy to do this if I was using a touch screen.
You should think though, is it really necessary to fit that much information on one screen? How many bars do you think would be appropriate on average to be able to fit in the vertical space of the screen? Perhaps you could have two modes - large and small, where large fits 30 rows, and small can fit many more.
But it's not really something you should be too concerned about at this stage. Just make sure that it is easy to change it later on, and you won't have to worry about it now. User testing should sort out the problems - as long as you listen to there needs (or watch them, see the mistakes they make, and try to fix the most common ones).
One thing to remember, is the "rule of 7", which basically means people are more comfortable looking at less information, as too much information can overload the brain (but it really depends on the target audience, for instance, an historian may rather see as many concurrent events at once).