True positive ratio

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. 

Sensitivity the ratio of true positives to total activities ... 

Many of the commonly used enrichment descriptors are based on two values. The first value is the sensitivity Se, true positive rate, Equation 3.3), which describes the ratio of the number of active molecules found by the VS method to the number of all active database compounds ... 

Sprinzak et al. (2003) found by a rigorous computation that the overall reliability of high throughput Y2H assay was about 50% (based on Ito and Uetz yeast proteome Y2H screening). The quality of an interaction was assessed with the potential co-localization or a possible common cellular role of the two proteins. This was integrated into a formula which determined the ratio of true positives. 

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.

The drawings incorporate also points and arrows. The points show the true peak height (and the true retention time as well). In cases of poor resolution it is impossible to set this point intuitively to the true position which is often below the sum curve. The arrows show the positions at which both peaks are separated into fractions of equal purity by preparative chromatography. The number above each arrow indicates the percentage purity level attained. These numbers, however, are only true if the ratio between the amount of material and the signal (peak height as... 

One measure of accuracy is the likelihood ratio (LR) [17]. The likelihood ratio is based on the relationship between the true positive fraction and the false positive fraction. Thus, LR = TPF/FPF. Substituting terms, the LR = sensitivity/(1-specificity). Receiver-operating characteristic curves are graphical summaries of likeli-... 

Enrichment metrics are frequently derived from ttvo basic values, the sensitivity (Se) and the specificity (Sp). Se or true positive rate is the ratio of the number of selected active molecules and the number of all biological active database molecules (5.1) [9, 65]. 

Figure 5.109 illustrates a calculation of the true draw ratio by following the changes of the cross-section at various positions along the fiber, starting at the point of initial necking. In Fig. 5.110 the true stress-strain curves are plotted as calculated... 

The ratio of warnings per true-positive warnings also shows an increase with increasing TTC... 

A 50% peptide probability can be used instead of the initial list of high-confidence identifications (99% protein confidence, 95% peptide confidence, and containing 2 unique peptides) in order to include peptides with lower Mascot scores that represent true positive identifications and would improve the overall spectral counting sensitivity. Ratios for proteins showing zero spectral counts in either control or treated groups should be tabulated as UC (unique in control) or UT (unique in treated). 

Experimental analog filters tend to skew the input function more or less toward longer times (in the direction of scanning). This is the price paid for an improved signal-to-noise ratio (SNR). For optimization of smoothing, one should start with the lowest possible time constant of the device and observe both the SNR and the attenuation as well as the A shifting of the main maximum (AA). The latter is particularly important if the true position of the extrema is desired. 

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]. 

Sensitivity. The ability of a test to detect the presence of disease, as determined by the ratio of true positives divided by the sum of true positives and false negatives. 

The ions so produced are separated by their mass-to-charge (m/z) ratios. For peptides and proteins, the intact molecules become protonated with a number (n) of protons (H+). Thus, instead of the true molecular mass (M), molecular ions have a mass of [M + uH]. More importantly, the ion has n positive charges resulting from addition of the n protons [M + uH]". Since the mass spectrometer does not measure mass directly but, rather, mass-to-charge (m/z) ratio, the measured m/z value is [M + uH]/u. This last value is less than the true molecular mass, depending on the value of n. If the ion of true mass 20,000 Da carries 10 protons, for example, then the m/z value measured would be (20,000 + 10)/10 = 2001. 

It should be noted that positional selectivity is never complete even when a clean reaction gives only one isolated product.Reaction occurs at all positions in proportion to the ratio of the rate constants. The difference between a clean reaction (e.g., rate 9 times that of a competing reaction) and one giving a troublesome mixture can be merely a moderate quantitative increase in one rate (e.g., to a 9 7 rate ratio) or a change in both rates (e.g., to a 3 4 ratio). Work such as that of Kauffmann and Boettcher on heteroarynes illustrates the potential of modern forms of chromatography for determining the true proportion of even very minor products. 

However, upon dissolution, an epimerization of the anions can occur in the presence of acidic counter-ions. This is particularly true for 16a-16d [39]. The nature of the solvent (MeOH, CHCI3) plays a crucial role on the kinetics of epimerization and the position of the resulting equilibrium. For anions made with a 2R, 3R) tartaric backbone, a A configuration is always preferred in MeOH the selectivity, obtained after a slow equilibration, being independent of the nature of the ester alkyl chain (diastereomeric ratio (d.r.) 3 1). However, in chloroform, the A diastereomer is rapidly obtained and the selectivity is best if the ester side chain is sterically demanding (d.r. 2 1 to 9 1 from 16a to 16d) (Scheme 16). 

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