Repeat readings

Table 9-1 Results from 20 repeat readings of 5 g of sample dissolved in 100 ml water...

Table 9-2 Results of repeat readings of six aliquots in six flasks (from 10-g samples)...

Before considering the design and the analysis of it in detail, let us take a look at the factors that are being included in the design, and their impact on the experimental design and the analysis of this design we have six samples, two methods of analysis for the constituent of interest, two laboratories, two chemists in each laboratory and five repeat readings of the constituents of each sample by each chemist. Statistical hypothesis... 

Accuracy is the ability of a balance to precisely and repeatedly read a weight. The ability for a balance to read a particular weight is based not only on the above attributes and characteristics, but also on three other factors ... 

For the efficient calculation of the residual vector g it is advantageous to process the operators J and K"" sequentially. Then, for a fixed operator label mn, one needs for a given iK all jL together in order to evaluate the vectors y and z . Unfortunately, it seems impossible to obtain the a. iK,jL) and ff (iKJL) in this order without repeatedly reading the yf/ or keeping them in high-speed memory. However, the coupling coefficients < K L >... 

The simplest procedure, and the one almost universally applied, is to perform repeat runs at a set of conditions to establish the presence and extent of (presumably) random error. The arithmetic average of this set of repeat readings is assumed to be a better approximation of the true value. Unfortunately, each reading adds a substantial unproductive burden to the experimental program so that repeat runs are few in any investigation. The preferred procedure is to perform a few runs at one convenient experimental condition, and to calculate some measure of error dispersion at that point. Since there are rarely enough repeat measurements at any other point to do a serious evaluation of the error, a simplistic measure such as the average error is often based on the error estimate at this one point ... 

Consider the case of the constant volume BR. Because of analytical constraints, in most cases only a few readings of composition are obtained in a run. There are no repeat readings at any point and the available data points are subject to errors of unknown magnitude. Because the rate of a reaction is a function of the temperature and concentration of reactants we will need to obtain rates at several reactant concentrations. This can be done in two ways ... 

When possible, it is good practice to make repeated readings of the same experimental conditions. For... 

In other situations, where there are multiple repeat readings for the jc,-values, the g values at a specific x,- can provide the estimate for the weights. In this example, an Si or s] would be calculated for each month, using the three replicates at each month. Because, at times, there was significant variability within each month, as well as between months (not in terms of proportionality), it probably would not have been as useful as the regression was. It is suggested that the reader make the determination by computing it... 

For each selected CWA, determine the minimum concentration levels (minimum detectable levels, MDLs) where repeatable readings are achieved using JSORs for point sampling devices as a guide for detection sensitivity objectives. The MDL... 

Repeated readings of these tubes recorded on a work sheet over a period of hours will show definite trends resulting from previous operation as well as existing conditions. In this way a clear picture of the rate and extent of the flux and temperature trends will provide accurate data for comparison with instrument performance. After an. even temperature balance is obtained by the temperature sampling method, outlet tube temperature points can be accurately adjusted on the deviation recorder to maintain or improve the flux distribution. 

The reference without repetition of the text is also worth mentioning. With this, the author of the contract protects himself against small modifications the other party may introduce in its own favour, hoping it may not be noticed. There is, in fact, a great risk of overlooking small modifications since the repeated reading of the same document makes one bhnd . 

Capacity measurements by discharge are most reliable and one would anticipate repeatable readings, but this is not always the case, especially with lead-acid batteries. Independent lab tests, including those at Cadex, have revealed differences in capacity readings of more than 10% under identical test conditions. The reason for this discrepancy is not fully understood other than to realize that batteries are electrochemical devices that exhibit human-like qualities. (Our IQ [intelligence quotient] level also diverges depending on time of day and other conditions.) These tolerances... 

---