A comparison of two methods to assess the usage of mobile hand-held communication devices
Berolo S, Steenstra I, Amick BC 3rd, Wells RP. A comparison of two methods to assess the usage of mobile hand-held communication devices. J Occup Environ Hyg. 2014 Dec 1:0. [Epub ahead of print]
Objective: The purposes of this study were to: 1) examine agreement between self-reported measures of mobile device use and direct measures of use, and 2) understand how respondents thought about their device use when they provided self-reports.
Methods: Self-reports of six categories of device use were obtained using a previously developed questionnaire, and direct measures of use were collected using a custom logging application (n = 47). Bland-Altman analyses were used to examine agreement between the two measurement approaches. Interviews targeted participants' experiences completing the device use section of the questionnaire.
Results: Self-reports of use on a typical day last week overestimated logged use; overestimates tended to be low at low average usage times, and became more variable as usage time increased. Self-reports of use yesterday also exceeded logged use, however the degree of overestimation was less than for a typical day last week. Six themes were identified from interviews, including the thought process used by participants to arrive at usage and the ease of reporting usage.
Discussion: It is challenging for respondents of this questionnaire to provide accurate self-reports of use. The source of this challenge may be attributed to the intrinsic difficulty of estimating use, partly due to the multiple functions of the devices as well as the variability of use both within a day and a week.
Conclusion: Research investigating the relationship between device use and health outcomes should include a logging application to examine exposure simultaneously with self-reports to better understand the sources of hazardous exposures.
Figure 2 demonstrates that in this population, generally speaking, participants’ self-reports overestimate their logged use. This figure shows a relationship between the difference and the average for each category of use; the difference between self-reported and logged use tends to be low at low average usage times, and becomes more variable as average usage time increases.
It was observed that, on average, self-reports exceeded logged use by 1.90 times for emailing, texting, and instant messaging; 2.25 times for scheduling; 3.16 times for internet browsing; 1.75 times for making calls and talking on the phone; 7.17 times for listening to music, watching videos, and taking pictures; and 2.72 times for gaming. The large average overestimate of 7.17 times for listening to music, watching videos, and taking pictures is likely due to characteristics of the logging application and is therefore not a true reflection of the possible overestimate.
The participants’ self-reports overestimated their logged use; overestimates tended to be low at low average usage times, and became more variable as average usage time increased.
Results from the present study show that on average, for a typical day in the last week, self-reports of phone use exceed logged use by a factor of 1.75. However, our results also show that, on average, self-reports of phone use “yesterday” slightly underestimated logged use.
The comparisons made in this study between self-reported and logged use were made among a small, restricted university sample.
Going forward, research investigating the relationship between mobile hand-held device use and health outcomes should include a logging application to examine exposure simultaneously with self-reports and observational approaches to better understand sources of hazardous exposures. When self-report is used, a short recall period is preferred.
Joel M. Moskowitz, Ph.D., Director
Center for Family and Community Health
School of Public Health
University of California, Berkeley
Electromagnetic Radiation Safety
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