Sub-group analyses

If an honest author describes the analysis of half a dozen different end-points or 20 sub-group analyses, one of which is significant, then the multiplicity is overt and an educated reader can be suitably cautious. However, the unscrupulous may conduct endless analyses and only report the one that hit the... 

Table 2.2 Sub-group analyses of clinical studies assessing the interaction between aspirin and ACE inhibitors...

However, it is impossible to say whether this represents a true effect, because the number of positive sub-group analyses in this study was the same as the number predicted by chance alone. Confirmatory evidence is required. ... 

Large-scale trials and meta-analysis of such trials are required to assess moderate treatment benefits. However, within trials or between trials within meta-analysis, sub-group analysis may result in spurious results due to the play of chance. Hence, it is important to avoid sub-group analyses to reduce the risk of spurious results except those sub-groups that have been pre-specified on the basis of some prior hypothesis. 

The lanthanide ions can be used to examine many of the potential properties of the A-sub group ions of the Periodic Table. The following is a list of some uses and properties of lanthanides which can be readily analysed... 

Data should not be broken down into multiple sub-groups unless either a Bonferroni correction or a distinction between primary and secondary analyses is used to provide additional protection. 

Fig. 8.7 The Biomarker Patterns Software. This supervised learning program performs multivariate analyses and creates tree-like structured decision diagrams by splitting the original data set into sub-groups of highest possible purity. The program calculates which signals (i.e., proteins) are best suited to act as splitters, and the splitting rules define what intensity (i.e., protein abundance) a signal must have to be sorted into one...

Members of this extensive and functionally diverse family of peptides that occur in arthropods show strong structural homology to each other, yet they can be sub-grouped on the basis of primary structure, as well as on preprohormone structure. Computer analyses, based on structural motifs of the mature peptides and their preprohormones, were carried out [134]. Thirty-two sequences were included in the analyses which showed that... 

Separation proceses based on liquid-gas interfaces can be divided into two major groups according to the manner in which they are connected to the analyser or instrument in their automation, namely off-line and on-line. Each of these groups can be in turn divided into sub-groups according to the analyte volatility and the use of heating and/or a reagent. 

Some parepistemes are pursued by small worldwide groups whose members all know each other, others involve vast communities which, to preserve their sanity, need to sub-classify themselves into numerous subsets. They all seem to share the feature, however, that they are not disciplines in the sense that I have analysed these... 

The extraction and clean-up methods used for the recovery of organophosphorus derivatives do not differ basically from those applied to other groups of substances. However, because of the high toxicity of the compounds involved, the techniques must be extremely sensitive and able to detect sub-nanogram amounts. A number of reviews have been published on the subject164-171. As previously mentioned, the compounds to be analysed may be found in living matter as well as in soil, sediments, water and air the experimental methods vary accordingly. 

Other acyl alkyl esters have been utilized only sporadically. Makita et al. [241] analysed N-isobutyloxycarbonyl methyl esters of protein amino acids. During the first step of the preparation, the amino group reacts with isobutyl chloroformate according to Scheme 5.21. The reaction is accomplished in 10 min in an aqueous medium in the presence of sodium carbonate at room temperature. Excess of the reagent is extracted with diethyl ether and the reaction mixture is saturated with NaCl, acidified with ortho-phosphoric acid to pH 1—2 and extracted with diethyl ether. Methanol is added to the ethereal extract and the carboxyl group is esterified with diazomethane at room temperature for 5 min, The solvent is removed under a stream of nitrogen at 50°C and the residue is dissolved in ethyl acetate. Arg does not provide a volatile derivative when sub-... 

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