True negative ratio

Specificity - TN/(TN + FP). This is also called the true negative ratio and is the opposite of the sensitivity. It is the probability that a case is correctly classified as not belonging to A. It is an important MP when it is crucial that this classification be the case. 

Specificity the ratio of true negatives to total inactives ... 

Figure IS-4 Simulated distributions of healthy and diseased populations. Note that the ratio of diseased patients to healthy patients, A to B, is less than I and very different at the point of decision (the likelihood ratio) from the ratio of TP to FP, which is much greater than i. TP, True positives TN, true negatives FP, false positives FN, false negatives.

Specificity is the measure of the true negative rate, which represents the ratio of true negatives (TN) to the total number of inactive compounds. The number of inactive compounds corresponds to both true negatives (TN) and false positives (FP) ... 

Sensitivity = TP/(TP + FN). This is also known as recall and as the true positive ratio. This is the number of cases correctly classified as belonging to A divided by the total number of cases that actually belong to A. Alternatively, it is the probability that a case will be correctly classified as belonging to A. It gives an indication of the relative number of false negatives and is an important PM when it is crucial that a case be correctly classified as belonging to A. For example, if a patient has cancer it is important that the patient be classified as having cancer. 

Successful VS rehes on the abihty to discriminate between active and inactive compounds in order to provide a set of compounds for experimental screening that is highly emiched in active molecules [93]. Sets of known active and inactive compounds are needed for the assessment of VS approaches. Decoys are molecules that are presumed to be inactive against a target, which can be used when too few inactive compounds are available for such testing [94]. Many metrics are currently used to quantify the effectiveness of a VS [95]. The enrichment factor (EF) represents one of the most prominent metrics in VS. EF measures how maity more active compounds are found within a defined early recognition fraction of the ordered list relative to a random distribution. Sensitivity and specificity are also descriptors that assess the enrichment of active molecules from a database. Sensitivity (Se, or true positive rate) describes the ratio of the number of active molecules found by the VS method to the number of all active compounds in the database. Specificity (Sp, or true negative rate) represents the ratio of the number of inactive compounds that were not selected by the VS protocol to the number of all inactive molecules included in the database [93]. 

Specificity. The ability of a test to prevent false detection of disease when it does not exist, as determined by the ratio of true negatives divided by the sum of true negatives and false positives. 

SPECIFICITY Refers to medical testing. The ability of a test to prevent the false detection of a specific condition. It is expressed as the ratio of (True Negatives)/(True Negatives + False Positives). (See also SENSITIVITY)... 

A second group of nanocomposites mentioned earlier is characterized by exhibiting negative deviations from the tortuous path model. These account for another significant number of composites. In these composites this negative deviation can be explained by one of two possible mechanisms. The first is the one mentioned in the previous example where tactoids predominate in the composite. In these cases the aspect ratio of the tactoids has not been determined but the data is compared to the tortuous path equation predictions utilizing the aspect ratio of the completely exfoliated clay. The solution in these cases is to utilize X-ray diffraction and electron microscopy to determine the true aspect ratio of the tactoids. This was done in the previous example. 

The pressure drop in the ductwork is first figured on the basis that no solids are present. This result is then corrected using Figure 8-1 1 to obtain the true pressure drop. The weight ratios of solids to air vary from 1 1 to 20 1. The flow rate of the solids in the positive-pressure system is much greater than for the typical negative system.37 The pressure drop in the fiber filters is generally about 4 in H20 (100 kg/m2), and that in cyclone separator varies from 1 to 3 in HzO (25-75 kg/m2).37... 

Negative accuracy the ratio of true to observed negatives ... 

A different electrochemical approach was applied to the cathodic reduction of sulfones in W,JV-dimethylformamide (Djeghidjegh et al., 1988), for example t-butyl phenyl sulfone, which is reduced at a more negative potential ( pc = -2.5 V) than is PBN (-2.4 V). Thus, the electrolysis of a mixture of PBN and the sulfone would possibly proceed via both true and inverted spin trapping. If a mediator of lower redox potential, such as anthracene (-2.0 V), was added and the electrolysis carried out at this potential, it was claimed that only the sulfone was reduced by anthracene - with formation of t-butyl radical and thus true spin trapping was observed. It is difficult to see how this can be reconciled with the Marcus theory, which predicts that anthracene - should react preferentially with PBN. The ratio of ET to PBN over sulfone is calculated to be 20 from equations (20) and (21), if both reactions are assumed to have the same A of 20 kcal mol-1. 

A ratio used to assess the degree of cooperativity exhibited by an enzyme. It is equal to the true Ymax value (typically extrapolated from the high-substrate-concen-tration end of a double-reciprocal plot) divided by the apparent Emax value obtained from extrapolating the asymptote in the low-substrate-concentration portion of the double-reciprocal plot. For a noncooperative system, Ry will equal one positively cooperative systems will have values greater than one and negatively cooperative systems will have values less than one . This method requires good estimates of the asymptotes. 

An interesting experiment is to allow oxidative phosphorylation to proceed until the mitochondria reach state 4 and to measure the phosphorylation state ratio Rp, which equals the value of [ATP] / [ADP][PJ that is attained. This mass action ratio, which has also been called the "phosphorylation ratio" or "phosphorylation potential" (see Chapter 6 and Eq. 6-29), often reaches values greater than 104-105 M 1 in the cytosol.164 An extrapolated value for a zero rate of ATP hydrolysis of log Rf) = 6.9 was estimated. This corresponds (Eq. 6-29) to an increase in group transfer potential (AG of hydrolysis of ATP) of 39 kj/mol. It follows that the overall value of AG for oxidation of NADH in the coupled electron transport chain is less negative than is AG. If synthesis of three molecules of ATP is coupled to electron transport, the system should reach an equilibrium when Rp = 106 4 at 25°C, the difference in AG and AG being 3RT In Rp = 3 x 5.708 x 6.4 = 110 kj mol-1. This value of Rp is, within experimental error, the same as the maximum value observed.165 There apparently is an almost true equilibrium among NADH, 02 and the adenylate system if the P/O ratio is 3. 

By signal averaging in repetitive experiments. This technique is useful when the noise is truly random so that positive and negative deviations from the true signal are equally likely. The S/N ratio increases then with the square root of the number of experiments... 

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