Reproducibility interval

The term reproducibility or reproducibility interval (R) is analogous to the term repeatability, but it is the maximum permissible difference between two results obtained on the same material but in different laboratories. Therefore, differences between two or more laboratories should not exceed the reproducibility interval more than five times in a hundred ... 

The specification of repeatability and reproducibility intervals, without specification of a statistical confidence level, weakens the precision and accuracy... 

In a double-blind study in 12 healthy volunteers, psilocybin 115 and 250 micrograms/kg significantly impaired their ability to reproduce interval durations longer than 2.5 seconds and to synchronize to inter-beat intervals longer than 2 seconds it also caused them to be slower in their preferred tapping rate (10). These objective effects on timing performance were accompanied by... 

The point at which an equivalent or stoichiometric amount of titrant is added is called the equivalence point. The point at which the reaction is observed to be complete is called the end point, that is, when a change in some property of the solution is detected. The end point should coincide with the equivalence point or be at a reproducible interval from it. 

Pressure and volume values converted, and entPalpy and entropy values reproduced, from Hust and Stewart, NBS TecP. Note 202, 1963. TPis source gives values at and above 72.373 K at closer pressure intervals, c = critical point. Tbe notation 1.268.-3 signifies 1.268 x 10" ... 

Fig. 83. IR spectra of K2NbF7 undergoing melting in an inert atmosphere (1 -820°C 2 - 880°C) and in weak vacuum (curves 3 and 4, 20-minute interval, 5 -800°C). (Reproduced from [363], A. I. Agulyansky, V. A. Bessonova, Zh. Neorg. Khim. 29 (1984) 79, Copyright 1984, with permission of Nauka (Russian Academy of Sciences) publishing.

Procedure. Place 45 mL of the supporting electrolyte in the cell and fill the isolated cathode compartment with the same solution to a level well above that in the cell. Pipette 5.00, 10.00, or 15.00 mL of the 0.01 M antimony solution into the cell and titrate coulometrically with a current of 40 milliamps. Stir the solution continuously by means of the magnetic stirrer and take e.m.f. readings of the Pt-S.C.E. electrode combination at suitable time intervals the readings may be somewhat erratic initially, but become steady and reproducible after about 3 minutes. Evaluate the end point of the titration from the graph of e.m.f. vs counter reading this shows a marked change of e.m.f. at the end point. If it proves difficult to locate the end point precisely, recourse may be made to the first- and second-differential plots. 

Discussion. The turbidity of a dilute barium sulphate suspension is difficult to reproduce it is therefore essential to adhere rigidly to the experimental procedure detailed below. The velocity of the precipitation, as well as the concentration of the reactants, must be controlled by adding (after all the other components are present) pure solid barium chloride of definite grain size. The rate of solution of the barium chloride controls the velocity of the reaction. Sodium chloride and hydrochloric acid are added before the precipitation in order to inhibit the growth of microcrystals of barium sulphate the optimum pH is maintained and minimises the effect of variable amounts of other electrolytes present in the sample upon the size of the suspended barium sulphate particles. A glycerol-ethanol solution helps to stabilise the turbidity. The reaction vessel is shaken gently in order to obtain a uniform particle size each vessel should be shaken at the same rate and the same number of times. The unknown must be treated exactly like the standard solution. The interval between the time of precipitation and measurement must be kept constant. 

Campbell (6) was perhaps the first to investigate the relationship between tenderometer values for raw peas and the texture characteristics of collateral samples after freezing and cooking. A high degree of correlation was observed. The investigations of Nielsen and co-workers (31) indicate the usefulness of the instrument for estimation of maturity in peas intended for freezing preservation. In order to secure consistent and reproducible results, the instrument requires standardization and calibration, and the measurements must be made under standardized conditions of temperature and interval after harvest. 

Figure 13. Cumulative probability for pit-generation time interval at constant potential of 18Cr-8Ni stainless steel in 0.2 kmol m 3 NaCl solution containing 0.1 kmol nf3 NajSO 23 o, = 0.85 V vs. SCE , =0.95 V vs. SCE. (From N. Sato, J. Etectrochem. Soc. 123, 1197, Fig. 2. Reproduced by permission of The Electrochemical Society, Inc.)...

It was demonstrated in Chapter 6 that impact theory is able to describe qualitatively the main features of the drastic transformations of gas-phase spectra into liquid ones for the case of a linear molecule. The corresponding NMR projection of spectral collapse is also reproduced qualitatively. Does this reflect any pronounced physical mechanism of molecular dynamics In particular, can molecular rotation in dense media be thought of as free during short time intervals, interrupted by much shorter collisions ... 

Figure 1.6. Repeatability and reproducibility are defined using historical data. The length of the time interval over which the parameter is reviewed is critical the shorter it is, the better defined the experimental boundary conditions tend to be the repeatability sets the limit on what could potentially be attained, the reproducibility defines what is attained in practice using a given set of instrumentation and SOPs.

The traditional arrangement of simple spherical glassware and Isomantles with full-power on-off controllers monitored by mercury thermometers, would still be widely recognised. So too would be the plug-shot piston pumps set up and monitored by use of measuring cylinders. Although tried and tested this hardware system requires constant attention by a skilled lab. technician to achieve control and reproducibility of even the first-order process parameters manual data collection is hardly feasible at better than 10-15 minute intervals. 

Apparently, the main idea behind this approach needs certain clarification. For example, formula (38) necessitates imposing a nonzero background temperature prior to the front. In spite of this fact, there are some delays in introducing new intervals, thus causing large deviations of a solution in a vicinity of the front. Formula (37) is useless for very large values of the index cr a > 20). Formula (36) has the best accuracy and reproduces rather accurately without concern of the background temperature. 

In the temperature interval 400-600 K the activation energy is determined to be 50 kj mol while in the regime 600-800 K it is only 27 kj mol . The researcher is very happy that he/she can reproduce the activation energy. Can you rationalize these findings and should the researcher be happy ... 

Figure 7.5 Rate recording of the dose-dependent inhibitory effects of apomorphine (pg/kg) on the spontaneous activity of a neuron in the medial prefrontal cortex of the halothane anaesthetised rat and its antagonism by haloperidol (HAL, 0.5mg/kg). Time scale is 50 min intervals. Reproduced by permission from Dailey (1992)...

The mixture was passed at 2 L/min through a glass cylinder (9 cm diam. x 35 cm) containing 3 rats or 4 mice. The effluent gas was analyzed for NO2 at hourly intervals by the Griess-Saltzmann reaction (8). Our results agreed closely with the value of 106 ppm for the NO2 cylinder, specified by the supplier. Atmospheric NO2 concentration varied in different experiments, partly on purpose and partly because the valve settings were not entirely reproducible. 

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