Blinding

Obviously, by virtue of having used concurrent controls, any observed difference between treatments in a clinical trial cannot be due to differences between trials. The patients being compared, irrespective of treatment, are in the same trial. This obvious point is worth labouring because it reinforces once again that the basic logic of clinical trials is comparative and not representative. If it were representative we should require patients who were typical the difference between patients from trial to trial would then not be an issue and we would not need concurrent controls. Nevertheless, even though the patients studied are studied in the same trial, there may be important differences between them. The purpose of randomization is to deal with this within-trial source of variation. It has nothing to do with differences between trials. 

Another reason is rather philosophical and has to do with replication of experiments. Suppose, for example, we insisted that in a clinical trial there was only one possible division of the patients into two groups that was acceptable. (Some division, perhaps, which made the two groups very evenly balanced in some way.) Having divided the 

Design and Interpretation of Clinical Trials as Seen by a Statistician 

To sum up. Randomization promotes confidence that we have acted in utmost good faith. It is not to be used as an excuse for ignoring the distribution of known prognostic factors. For a randomized trial, however, our probability calculations make an appropriate allowance for the distribution of unknown factors. 

Randomization is also essential for effective blinding of a clinical trial. 

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Classifier structures resulting from the training were verified in a blind test. To evaluate the reliability and performance of the NSC it was subjected to a blind test using unknown data containing spectra measured for various sizes and locations of the disbonds (from 50% to over 100% of the probe size). 

Table 1 Blind test results for "Lower wing skin" using network with 2 hidden nodes and training for 2000 iterations...

Blind test data was classified 100% correctly between flawless and defect samples. Layer containing flaw was determined correctly in 97.2% of the cases (see Table 2 for details). 

Table 2 Blind test results (54 spectra) using final networks obtainedfrom training set TS I.

Muns ENDOR mvolves observation of the stimulated echo intensity as a fimction of the frequency of an RE Ti-pulse applied between tlie second and third MW pulse. In contrast to the Davies ENDOR experiment, the Mims-ENDOR sequence does not require selective MW pulses. For a detailed description of the polarization transfer in a Mims-type experiment the reader is referred to the literature [43]. Just as with three-pulse ESEEM, blind spots can occur in ENDOR spectra measured using Muns method. To avoid the possibility of missing lines it is therefore essential to repeat the experiment with different values of the pulse spacing Detection of the echo intensity as a fimction of the RE frequency and x yields a real two-dimensional experiment. An FT of the x-domain will yield cross-peaks in the 2D-FT-ENDOR spectrum which correlate different ENDOR transitions belonging to the same nucleus. One advantage of Mims ENDOR over Davies ENDOR is its larger echo intensity because more spins due to the nonselective excitation are involved in the fomiation of the echo. 

Methanol is a colorless liquid boiling at 65°C and is miscible with water m all proportions It is poisonous drinking as little as 30 mL has been fatal Smaller amounts can produce blindness... 

Xylene cyanole-methyl orange indicator, Schoepfie modification (for partially color blind operators) dissolve 0.75 g xylene cyanole FT (Eastman No. T 1579) and 1.50 g methyl orange in 1 liter of water. 

Single-operator characteristics are determined by analyzing a sample whose concentration of analyte is known to the analyst. The second step in verifying a method is the blind analysis of standard samples where the analyte s concentration remains unknown to the analyst. The standard sample is analyzed several times, and the average concentration of the analyte is determined. This value should be within three, and preferably two standard deviations (as determined from the single-operator characteristics) of the analyte s known concentration. 

Agency. A second example of an external method of quality assessment is the voluntary participation of the laboratory in a collaborative test (Chapter 14) sponsored by a professional organization such as the Association of Official Analytical Chemists. Finally, individuals contracting with a laboratory can perform their own external quality assessment by submitting blind duplicate samples and blind standard samples to the laboratory for analysis. If the results for the quality assessment samples are unacceptable, then there is good reason to consider the results suspect for other samples provided by the laboratory. 

One drawback of time bins relates to the events they record. If two or more ions arrive at the array detector at the same instant, the resulting electrical pulse is the same as if only one ion had arrived. The bins are blind to multiple concurrent events. 

Full eye protection should be worn whenever handling acryhc monomers contact lenses must never be worn. Prolonged exposure to Hquid or vapor can result in permanent eye damage or blindness. Excessive exposure to vapors causes nose and throat irritation, headaches, nausea, vomiting, and dizziness or drowsiness (solvent narcosis). Overexposure may cause central nervous system depression. Both proper respiratory protection and good ventilation are necessary wherever the possibiHty of high vapor concentration arises. 

Color Additives. Color additives, for the benefit of dog and cat owners, help simulate food richness, which is evaluated ia many differeat ways. The additioa of color helps minimi2e variatioas ia appearance associated with batch difference ia food iagredieats and fineness of gtind. Cats and dogs are practically color blind colors have Utfle influence on them. 

The type of floe requited depends on the separation process which foUows, eg, rotary vacuum filtration requites evenly sized, smaU, strong floes that capture ultrafines to prevent cloth blinding and cloudy filtrates. The floes should not be subject to sedimentation in the vat or breakage by the agitator. 

Addition of Inert Filter Aids. FUtet aids ate rigid, porous, and highly permeable powders added to feed suspensions to extend the appheabUity of surface filtration. Very dilute or very fine and slimy suspensions ate too difficult to filter by cake filtration due to fast pressure build-up and medium blinding addition of filter aids can alleviate such problems. Filter aids can be used in either or both of two modes of operation, ie, to form a precoat which then acts as a filter medium on a coarse support material called a septum, or to be mixed with the feed suspension as body feed to increase the permeabihty of the resulting cake. 

The benefits of prethickening can be summarized as an increase in dry cake production, reduction in specific cake resistance, clearer filtrate, and less cloth blinding. 

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