Replication software packages

Determination of sodium in a soil extract. Using the five sodium calibration standards already prepared obtain five replicate readings for each sodium standard and calculate the mean emission intensity and RSD for each standard. Aspirate the standards in ascending and descending order of concentration. Aspirate a blank between each standard and zero the instrument. Using a statistical software package construct a... 

Closely related strains of bacteria yield highly similar mass spectra (Fig. 6.5). To reliably characterize strains, the reprodneibility of replicated mass spectra of the same strain must be quantified before condneting further analysis. Here, reproducibility refers to how similar replicate spectra of the same strain are to one another based on comparing peak presence/absence and/or peak intensity. Reprodneibility (similarity) between replicates of the same strain must exceed the similarity of mass profiles of closely related bacterial strains. Several previous studies have examined reprodneibility based primarily on visnal inspection of spectra (Arnold and Reilly 1998 Jackson et al. 2005), while more recently, studies have quantified reproducibility more rigorously using software packages described previously. The coefficient of... 

The replicate measurements (at least two each time) are made over a prolonged period of time (at least 40 times), on a check-standard sample which must remain constant and homogeneous during the measurement cycle. Software packages are available to assist in the evaluation of results and in plotting the control charts, and any measurements outside the control limits are automatically highlighted. Visual inspection of the charts may reveal systematic trends on drifts. The variability is then analysed, its causes identified and brought under control and reduced. 

If (true) replicates for the standards are available, it is possible to check whether the variances of the residuals at the different concentration levels are comparable (one of the assumptions of the simple least squares fit). Several tests are popular for this and they are reviewed below and implemented in many statistical software packages. 

Estimated standard deviations are easily obtained using a calculator that incorporates statistical function keys or with one of the many computer software packages. It is, however, useful to be able to perform a stepwise arithmetic calculation, and an example using the set of five replicate titers by analyst A... 

A software package that was developed by Stat-Ease, Design Expert Version 6.0, was used to design the test array and to manipulate the data analysis. We replicated each point with three samples and we also ran three midpoint sets in this study. 

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