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Biomedical subjects

N Kazantzis

Publications and source records attributed to N Kazantzis.

4 recordsLinked to original sources
PubMed2001

Concluding causation from correlation: comment on Burns and Spangler (2000).

This commentary critiques the study conducted by D. D. Burns and D. Spangler (2000) in which the relationship between homework compliance and therapy outcome was estimated using structural equation modeling (SEM). Although the authors of the commentary advocate the use of SEM, they suggest greater caution in the indiscriminate endorsement of a causal relationship based on (a) correlational data and (b) retrospective accounts of the main predictor variable within a cross-sectional design. This discussion also highlights a need to address the issue of therapist competence in homework administration. The results of Burns and Spangler's report are consistent with existing empirical evidence suggesting that compliance with homework facilitates therapeutic outcome. However, the gold standard for determining causal inferences rests on prospective, experimental research rather than on retrospective, correlational models.

Humans↗
PubMed2000

Power to detect homework effects in psychotherapy outcome research.

Studies of homework effects in psychotherapy outcome have produced inconsistent results. Although these findings may reflect the comparability of psychotherapy with and without homework assignments, many of these studies may not have been sensitive enough to detect the effects sizes (ESs) likely to be found when examining homework effects. The present study evaluated the power of homework research and showed that, on average, current power levels are relatively weak in controlled studies ranging from 0.58 for large ESs to 0.09 for small ESs. Thus, inconsistent findings between studies may very well be due to low statistical power.

Bias↗
PubMed1998

Acute effects of 50 Hz, 100 microT magnetic field exposure on visual duration discrimination at two different times of the day.

A two-alternative, forced-choice visual duration discrimination task was used to examine the effect of an intermittent, 50 Hz, 100 microT magnetic field on accuracy at two different times of the day. A total of 59 female and 40 male subjects with an age range of 18 to 46 years were studied under both field-exposed and sham-exposed conditions. The subject's task was to decide which of two sequentially presented light flashes had the longer duration, percentage correct being the measure of performance. The data were gathered under double-blind conditions with sham and real exposure counterbalanced. Exposure to the magnetic field produced a small improvement in accuracy but only at the most difficult level of the task, with female subjects showing a larger improvement than males. The time of day at which the study was run had no effect on performance. Despite the relatively large number of subjects used and a relaxed alpha level (P = .3), the statistical power of the test to detect the observed effect was still only 0.71.

Adolescent↗