Scenario 4 – User-Interface Design

Technology is becoming increasingly smaller and the computer industry is faced with the problem of designing user-interfaces that are perceptually clear and informative to users. As part of your role within a large IT company, you have been tasked with developing a set of guidelines that will inform the optimal icon size for small displays. You turn to the Method of Adjustment to identify the optimal icon size. In your experiment, you present volunteers with either a very small icon, or a very large icon, and they have to adjust it to what they feel is an optimal size for the display in question. Optimal in this case refers to their ability to recognise the icon when it is as small as possible. Here is a set of measurements from one volunteer

Trial Number	1	2	3	4	5	6	7	8	9	10	11	12
Icon Size (width in pixels)	24	20	24	21	19	19	21	20	26	25	18	17

Calculate the threshold icon size.

Why did you have two different types of trials (one starting with very small stimuli, and the other starting with very large stimuli)?

If you had been calculating difference thresholds, which statistical value would provide an estimate of that threshold?

Comment on how accurate this threshold estimate is relative to estimates derived by other methods. If you wanted the most accurate estimate of the threshold icon size, outline an approach you might have adopted.