Prototype modeling & printed

The prototype was modeled and in the form of a ring. The ring was divided into two parts and a neodymium magnet would be placed both in the upper part and the floor part so that the devices can be exchanged easily. The width of each ring ranges between 10mm to 15mm so that it can bear the trackpoint with a diameter of 8mm. Three circumferences of the rings were chosen from the statistical anthropometric data.

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Fitts’ Law

We reviewed a paper called “Towards a standard for pointing device evaluation, perspectives on 27 years of Fitts’ law research in HCI” to refer on evaluation of our devices.

• In one experiment, multiple ID values should be shown. Each condition should be shown from 15 to 25 times.
• Movement Time (MT) needs to be measured, while the time used to move the pointing device (homing time, dwell time and etc.) should be eliminated.
• Scatter of subject’s movement end-points should be gathered by either determining the error rate or recording the physical end-points. This is to ensure that no data is filtered and conduct accuracy of adjustment.
• Throughput: overall measure of performance. In addition, Movement Time(means for each ID condition), error rates(per condition), end-point variation(standard deviation of end-point position per condition)

Conclusion: Error rate -> effective width -> effective index of difficulty -> movement Time -> Throughput

Mentor meeting

We asked our mentor TAs some questions about the paper and our experimental plan.

1. How to measure end-point scatter data?
   • Set the standard as distance between target and user’s selection. If the input system is good, the precision/accuracy should be high so the standard deviation will be low. On the other hand, error rates could be calculated only using success and failure.
2. Specific experimental design?
   • About three target sizes and a couple of distance types could be used. One set of experiment could be divided into a number of blocks so that participants can be given break time.
   • 7 subjects per device would be enough, even when considering an outlier.
   • No need to consider gender problems (but try to match the ratio) but think about eyesight problems (glasses)
   • If the trial fails, it should be done again; the subject should be informed in advance that they should do their best in order to lessen time
3. Things to be measured on HoloLens?
   • error rate: (number of failures) / (number of total trials)
   • The distance between the center of each target and the end-point