Non-response bias

A Chi-square test is conducted to check non-response bias. The results (see Table 7.2) show that there is no significant difference between the first-wave and second/third-wave respondents by aU three categories (i.e., SIC code, firm size, and job title) at the level of 0.1. It exhibits that received questionnaires from respondents represent an unbiased sample. 

Sanders Do non-cumulative dos response studies have any effect on your Ca2+ force curves In other words, do you bias your data by doing cumulative doso-response curves towards Ca2+ sensitization When there is a short exposure to the compound do you get a shift ... 

This option assumes a comparable or even standard placebo response rate for historical data and the current trial. The historical improvement rate (on placebo or without any treatment) is then used for purposes of comparison with results of subsequent non-placebo-controlled studies involving the same investigator and protocol design but different drugs. For historical placebo response data it is recommended that a small placebo treatment arm is used for safety data purposes and to avoid observer bias although this proposal may resolve or diminish some ethical concerns, it raises a number of scientific problems ... 

The dielectric susceptibility x is related to the relative dielectric constant er by x = er — 1 Equations (1.4) are only valid for small fields. Large amplitudes of the ac field lead to strong non-linearities in dielectrics, and to sub-loops of the hysteresis in ferroelectrics. Furthermore, the dielectric response depends on the bias fields as shown in Figure 1.4. From the device point of view this effect achieves the potential of a tunable dielectric behavior, e. g. for varactors. 

In a retrospective review of 37 patients with chronic non-malignant pain (mostly from failed lumbosacral spine surgery) treated with intrathecal hydromorphone there was an analgesic response in six of the 16 patients who were switched from morphine to hydromorphone because of poor pain relief (1). Opioid-related adverse effects, such as nausea, vomiting, pruritus, and sedation, were also reduced by hydromorphone in the 21 patients who were switched to hydromorphone because of morphine-related adverse effects, especially 1 month after use. These results should be treated cautiously, because of the limitations of a retrospective study that lacks strict inclusion criteria, with obvious population bias and under-reporting, and without standardized procedures for rotation to hydromorphone. 

Selectivity describes the ability of an assay to produce a measurable response only for the analyte of interest. Interferences are considered to be any factor causing a bias in the assay result and can be divided in two major groups specific and non-specific, as will be described below. 

Culture also plays a major role. For instance, physician bias, placebo effects, compliance factors, and patient beliefs and expectations all can influence the clinical effects of psychotropic agents (Smith et al. 1993). It has been reported that because of psychiatric practitioner bias, severe psychiatric illnesses are often diagnosed in African American patients, who are then prescribed high doses of neuroleptics (Price et al. 1985). It has also been reported that Caucasians tend to be more responsive than non-Caucasians to placebo (Escobar and Tuason 1980). 

Fulk (1995) usefully identifies two types of variability (random and systematic error) and three ways in which this may become manifest (within-test, within-laboratory and between laboratories). In a conventional concentration-response experiment, the random occurrence of variability within an experiment will give rise to error around the fitted regression line, i.e. it will make the estimate of toxicity less precise. By contrast, non-random occurrence of these factors between experiments or laboratories can result in different estimates of toxicity, leading to bias. However, testing on different occasions or in different laboratories is also subject to random errors. As a result, the variability that we see is usually a combination of random and systematic errors. Variability resulting from random errors is, by definition, difficult to address but systematic errors can be... 

An independent body (a review board or a committee, institutional, regional or national), constituted of medical professionals and non-medical members, whose responsibility is to verify that the safety, integrity and human rights of the subjects participating in a particular trial are protected and to consider the general ethics of the trial, thereby providing public reassurance. Ethics committees should be constituted and operated so that their tasks can be executed free from bias and from any influence of those who are conducting the trial. 

---