Availability Bias

Furthermore, with this approach it s possible to go in blind, without prejudging which targets may be present and what type of compounds should hit them, which may be more likely to result in the discovery of new targets and novel compounds if it finds anything at all. In cases where such information isn t known this sort of phenomenological approach may be the only way to go. But if target information is available, bias can still be built in if desired. 

The problem is that diversity space tends to be so huge that precious little of it is actually sampled by even the best diversity library. And, as pointed out by Dr Lipinski, practical limitations like chemistry success, selection bias, and reagent availability bias mean that true diversity just does not exist experimentally. High-throughput screening of diversity libraries is still routinely used and can produce hits, but no one should assume that it s more likely to do so than other methods. 

Availability bias An event is judged likely or frequent if it is easy to imagine or recall under relevant circumstances. However, it may result in a systematic overestimation of probabilities for events recently experienced, emotionally salient, or otherwise memorable or imaginable. For example, in a study by Lichtenstein et al. (1978) it was found that (1) the probabilities of dramatic, well publicized events such as botulism, tornadoes, motor-vehicle accidents, homicides, and cancer were overestimated, and (2) correspondingly unremarkable or less dramatic events such as asthma, diabetes, and emphysema were underestimated. Additionally, it was confirmed in the studies of shunters and construction workers by Zimolong (1979, 1985) that (3) hazards frequently experienced by the job incumbent... 

Recency is the tendency to rely on those data that are most readily available (e.g., most salient or recent) and therefore easiest to remember, while neglecting less readily available data. Availability bias and anchoring are the most frequent biases at work in hectic, high-pressure environments such as the emergency room. ... 

Available Bias Voltage. If the available bias supply voltage is less than the optimum or recommended bias voltage, large voltage drops across the load cannot be tolerated. The maximum responsivity in this case will be obtained when the load resistor equals the detector resistance. 

Availability bias is a mental shortcut in which people assess the frequency of a class or the probability of an event by the ease with which instances or occurrences can be brought to mind in order to make judgments about the probability of events. It operates on the notion that if you can think of it, it must be important. The availability of consequences associated with an action is positively related to perceptions of the magnitude of the consequences of that action. In other words, the easier it is to recall the consequences of something, the bigger we perceive these consequences to be. Because the frequency with which events come to mind is usually not an accurate reflection of their actual probability in reality, this leads to errors in judgment. 

Availability bias is a product of familiarity and salience. A General Practitioner is more likely to diagnose the next patient he sees with strep throat if several cases arrived in the office that day, due to the familiarity of the occurrence. Also, patients show up in emergency rooms reporting illnesses related to food poisoning more often than usual if news reports of food poisoning make it to the airwaves. 

The Shuttle Challenger disaster represents a real-world example in which an organization, NASA, allowed the bridge between systems engineering and safety that had existed throughout NASA s history, from Mercury to Gemini to Apollo and on to the early development of the shuttle, to collapse. The Safety Breakdown Theory in this case was the result of several biases that contributed to the failure. As described in Chapter 6, The Glismann Effect—in the form of Pressure bias. Feedback bias, and Availability bias—was obviously present ... 

Not so for synthesis in the chemical industry where a compound must be prepared not only on a large scale but at low cost There is a pronounced bias toward reactants and reagents that are both abundant and inexpensive The oxidizing agent of choice for example in the chemical industry is O2 and extensive research has been devoted to develop mg catalysts for preparing various compounds by air oxidation of readily available starting materials To illustrate air and ethylene are the reactants for the industrial preparation of both acetaldehyde and ethylene oxide Which of the two products is ob tamed depends on the catalyst employed... 

Sometimes just one determination is available on each of several known materials similar in composition. A single determination by each of two procedures (or two analysts) on a series of material may be used to test for a relative bias between the two methods, as in Example 2.4. Of course, the average difference does not throw any light on which procedure has the larger constant error. It only supplies a test as to whether the two procedures are in disagreement. 

Analytical and Test Methods. Many of the procedures for technical analyses of magnesium hydroxide are readily available from the principal producers. These procedures should be carefully reviewed. Site-specific variations in procedure steps and mechanics, especially for chemical activity, can bias results and inadvertantiy disqualify an otherwise acceptable product. 

The third interaction compromising the parameter estimate is due to bias in the model. If noncondensables blanket a section of the exchanger such that no heat transfer occurs in that section, the estimated heat-transfer coefficient based on a model assuming all of the area is available will be erroneous. 

The schematic model is depicted in Fig. 8. As the bias voltage increases, the number of the molecular orbitals available for conduction also increases (Fig. 8) and it results in the step-wise increase in the current. It was also found that the conductance peak plotted vs. the bias voltage decreases and broadens with increasing temperature to ca. 1 K. This fact supports the idea that transport of carriers from one electrode to another can take place through one molecular orbital delocalising over whole length of the CNT, or at least the distance between two electrodes (140 nm). In other words, individual CNTs work as coherent quantum wires. 

Fig. 8. Schematic illustration of the tunnelling in a CNT-based device (a) under no bias voltage, there are no orbitals available for conduction, (b) with small bias voltage, only one molecular orbital of a CNT contributes to the carrier transport and (c) when the next molecular orbital enters the bias window, current increases stepwise. Gate voltage can shift all the orbitals upward or downward. AE indicates the energy separation of molecular orbitals.

Also, the statistics available on materials are often presented so as to favor a particular bias, which complicates the process of... 

The Math As is immediately apparent, a mean cannot coincide with a SL if all measurements that go into it must also conform (cf. Fig. 2.13, distribution for p = 0.5), unless = 0. Any attempt to limit the individual measurements to the specification interval will result in a narrowing of the available margin for error in Xmean, be it manufacturing bias or inhomogeneity. This may be acceptable as long as one has the luxury of 90-110% release limits, but becomes impracticable if these are reduced to 95-105%. 

The inherent reproducibility or imprecision of the method will have been determined as part of the validation procedure. This information can then be applied to the internal quality control programme which is designed to identify the intrusion of a bias (inaccuracy) and/or an alteration in the reproducibility of the assay. Programs for Internal quality control are most extensively developed for clinical laboratories because of the availability of suitable RMs in large batches and at an affordable cost although some level of IQC is appropriate to aU work carried out at a continuing basis see Section 6.2. 

Similarly, some INAA data contributed to the derivation of a reference value for Ba in SDO-i were biased high by an interference from Ru (Wandless 1993). The Ru is a fission product of U, whose concentration of 40 qg/g is relatively high in SDO-1. In this case, no appropriate reference sample was available for analysis to control the SDO-1 results the interference was identified through the disagreement between INAA data and data produced using XRF and ICP-AES methods on the same sample. A bias-free method again resulted when analysis of an atypical type led to detection of a rarely encountered but sizeable spectral overlap. Once identified, correction was straightforward. 

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