Linked by Thom Holwerda on Sun 24th Jun 2007 13:44 UTC
Federkiel writes: "People working with Apple computers are used to a very consistent user experience. For a large part this stems from the fact that the Lisa type of GUI does not have the fight between MDI and SDI. The question simply never arises, because the Lisa type of GUI does not offer the choice to create either of both; it's something different all along. I usually think of it as 'MDI on steroids unified with a window manager'. It virtually includes all benefits of a SDI and and the benefits of an MDI." Read on for how I feel about this age-old discussion.
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RE: Fitt's Law
by RandomGuy on Sun 24th Jun 2007 18:26 UTC in reply to "Fitt's Law"

Member since:
2006-07-30

Unfortunately, like Thom said, it doesn't take training into account.

Oh, it does take training into account but not explicitly.
The general formula "T=a+b*log2(D/W +1)" is the same for trained and untrained but the constant "b" would be a lot lower if you're trained to using this interface.

Let me explain what this means by a simple example:
Let's say we have a 1cm target (W=1) 30cms away from your pointer (D=30). This yields:
T=a+b*log2(31)=a+b*5

"b" could be 1 for a very inexperienced user and 0.1 for a trained user. "a" is probably mainly the reaction time + time needed to decide which button to hit, somewhere between 0.2 and 1s.
Let's say it's 0.3 for the pro and 1 for the noob.

noob: T=1+1*5=6s
pro: T=0.3+0.1*5=0.8s
So our pro could still be 7-8 times faster, all within the mechanics of Fitt's law.

Now let's say the target was 2cm and 10cm away:

noob: T=1+1*log2(10/2 + 1)=3.6s
pro: T=0.3+0.1*log2(10/2 +1)=0.6s

While the pro would still be 6 times faster, he would also be 33% faster than with the smaller target at a bigger distance.
Of course, the noob would be 1.7 times faster so any change in UI layout has the biggest effects on noobs.

So while the influence of Fitt's law is most easily seen for noobs, it is still valid for a trained person.

Edited 2007-06-24 18:30 UTC

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