Can people operate touch screen devices more quickly with their index finger or their thumb? Holding the device in landscape or portrait position? The article “Evaluation of a Psychomotor Vigilance Task (PVT) for Touch Screen Devices” (Hum. Factors 2017: 661–670) describes a study in which 13 participants performed a series of tasks on an iPod holding it two different ways: (1) In portrait position using their index finger and (2) In landscape position using their thumb. The median response time, in milliseconds, was recorded for each participant under both settings. Those observations are summarized in the accompanying table.

Test whether the results under the two positions are significantly different at the .05 significance level.

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iPod position Portrait/index Landscape/thumb Difference Mean 224.09 211.50 12.59 SD 39.30 30.74 15.28