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Are there any quantitative experiments that have studied (or that can be used to study) the usability of the trackpad vs the mouse, for the task of point and click?

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Say, for example, that we choose as a usability metric the time it takes a user to move the mouse pointer to a specific location on the screen and click on it. Are humans more accurate (measurable in terms of speed) moving a finger on their trackpad to the desired location, or moving a mouse (assuming a modern mouse)?

What experiments/software can a user do to measure this? I imagine that a tool that places random boxes around the screen and that tracks the time it takes the user to click on them, on average, would suffice.

Any thoughts?

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2 Answers 2

up vote 3 down vote accepted

Fitts's Law is the thing you want to test.

Fitts's law (often cited as Fitts' law) is a model of human movement primarily used in human–computer interaction and ergonomics that predicts that the time required to rapidly move to a target area is a function of the distance to the target and the size of the target. Fitts's law is used to model the act of pointing, either by physically touching an object with a hand or finger, or virtually, by pointing to an object on a computer monitor using a pointing device. It was proposed by Paul Fitts in 1954.

The law is expressed as a formula, where a and b are coefficients which are peculiar to the pointing device and/or context, and thus it can take different time with different pointing tools.

enter image description here


Here is an interactive tutorial on Fitt's Law, which includes reporting the average times it takes you to click a series of targets.

You can run through this tutorial for each of your pointer methods, and take note of the measured times it reports.

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oh, btw that interactive doesn't work on iOS, possibly because it uses Flash. –  Erics Mar 15 at 19:17
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As Erics said: use Fitts Law. As for the experiment, the industry accepted standard is available in ISO 9241-9. It uses Fitts Law and throughput for calculation You can find one Java implementation here. If you're interested in reading a little bit more on why use the standard, I recommend this paper. If you wish to build your own experiment and completely ignore the ISO standard, that is fine too. Just make sure to use average throughput as the measure. Throughput per trial is calculated as Index of Difficulty / Movement Time. While Index of Difficulty is measured as the (1 + log2 (Width / Distance))

Note that this gives performance evaluation, but not accuracy. Accuracy is a different beast altogether which I don't believe you need.

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