"These forces are battling to a standstill, so that confidence measures are stable".
As previously reported [ 39, 47], behavioural measures were stable and reproducible over the testing period.
This study has, however, shown for the first time that BP measures are stable over a 16-week period and do not exhibit a placebo response.
As there is evidence that 2D : 4D measures are stable over time (McIntyre et al, 2006; Trivers et al, 2006), we consider it appropriate to analyse these data prospectively, despite the retrospective collection of 2D : 4D.
GEE was used to assess the relationship between 1 min means of contrast thresholds (contrast threshold1-min averages) and accommodation responses (accommodation response1-min averages) with time (min 1 7) to ascertain if the two sets of response measures were stable.
Because some practices' relative performance ranking varied considerably based on immediate versus delayed measurement, consumers of performance rankings, such as the U.S. Center for Medicare and Medicaid Services (CMS), need to carefully consider whether such measures are stable enough to serve as a basis for financial reward or penalization.
As proved in [32], this measure is stable for p≥2 and unstable for p equal to 0 or 1. Method S uses the order-2 measure, since two is the smallest integer power that implies stability.
This suggests that the measure is stable during a period when little change is expected.
Criteria a biomarker needs to meet are that it changes as a function of the process being monitored, can be accurately measured; is stable and does not show diurnal variations, correlates with exercise intensity, and is present in detectable amounts in easily accessible biological fluids [ 10].
We speculate that test-retest reliability can be influenced by the retest interval, the number of items on a subscale, the acuity of the patients tested; and the extent to which the construct being measured is stable and definable by patients.
