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  • Occupational Health and Environmental Toxicology  (3)
  • Wiley-Blackwell  (3)
  • Blackwell Publishing Ltd
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 17 (1996), S. 131-137 
    ISSN: 0197-8462
    Keywords: statistical power ; duration discrimination ; blood pressure ; heart rate ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: One hundred subjects, males and females with ages ranging between 18 and 48 years, were studied under both field-exposed and sham-exposed conditions. A 50 Hz, 100 μT magnetic field (MF) was used. To examine the effect of field exposure on performance, a two-alternative, forced-choice, duration-discrimination task with three levels of difficulty was used. The subject's task was to decide which of two sequentially presented light flashes had the longer duration. The standard duration was 50 ms, and the alternative durations were 65, 100, or 125 ms. Both reaction time and percentage of correct responses were recorded for each subject. MF and sham exposure were for 9 min each. Blood pressure and heart rate were also measured before and following MF exposure and sham-exposure trials. The study was performed double blind, with the exposure order counterbalanced. Compared to sham exposure, MF exposure significantly decreased reaction time on the hardest level of the performance task. MF exposure did not reliably affect percentage correct or cardiovascular performance. It was demonstrated that a relatively high level of statistical power was the basis for the observed MF effect, and the need to pay closer attention to power levels in future research is discussed. © 1996 Wiley-Liss, Inc.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 16 (1995), S. 317-323 
    ISSN: 0197-8462
    Keywords: human performance ; statistical power ; parametric resonance theory ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Two double-blind studies were run in an attempt to confirm the finding that a 0.2 Hz magnetic field affects simple reaction time (RT) in humans, whereas a 0.1 Hz field does not. In the first experiment, 12 volunteer subjects were exposed to a continuous 0.2 Hz, 0.1 Hz, or sham field in a fully counter-balanced, within-subjects design. Subjects were run singly for one condition each day over 3 consecutive days with a field strength of 1.1 mT and a daily exposure duration of 5 min. Neither magnetic field had any effect on RT at any time during the exposure. One condition of a second study, using a new group of 24 volunteer subjects, also failed to find any field effects at 0.2 Hz. Additionally, the second study failed to show any effects when the frequency, flux density, and field orientation were set according to parametric resonance theory. It is suggested that, although ELF magnetic field effects on human behaviour may be elusive, future research can improve detection rates by paying greater attention to reducing error variance and increasing statistical power. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 17 (1996), S. 274-278 
    ISSN: 0197-8462
    Keywords: power survey ; sample size ; effect size ; alpha level ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Research examining the effects of electromagnetic fields (EMFs) on human performance and physiology has produced inconsistent results; this might be attributable to low statistical power. Statistical power refers to the probability of obtaining a statistically significant result, given the fact that a real effect exists. The results of a survey of published investigations of the effects of EMFs on human performance and physiology show that statistical power levels are very low, ranging from a mean of.08 for small effect sizes to .46 for large effect sizes. Implications of these findings for the interpretation of results are discussed along with suggestions for increasing statistical power. © 1996 Wiley-Liss, Inc.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
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