Experimental replication

Odling N. W. A. (1995) An experimental replication of upper-mantle metasomatism. Nature 373, 58-60. 

Samples taken from the same experimental unit must not be considered as experimental replicates. 

Discuss the two methods used to ensure a uniform temperature among experimental replicates during a FIFRA microcosm experiment. 

Fig. 3 Cellulose, hemicellulose, and lignin content of progeny in families 99202 (a-c), 99217 (d-l), and 99239 (g-i). Bars indicate mean SE of three experimental replicates, each of which was analyzed using three instrumental replicates. Jf-Axis indicates the clone IDs for specific progeny individuals in each lanuly...

Fig. 4 Cellulose (a), hemicellu-lose (b), and lignin (c) content of different aged biomass samples from the reference clones. IVhile bars represent 1 year growth after eoppice black bars represent 3-year growth after coppice. Bars indicate the mean SE of three experimental replicates, each of which was analyzed using three instrumental replieates...

Figure 9.13 Residues of alachlor recovered from Little Cherry soil following apphcations in the field on (a) 27 September 1990, (b) October 1990, (c) 21 November 1990, and (d) 11 April 1991., experimental replicates , predicted. [Reproduced with permission from A. Walker, Y. Moon, and S. J. Welch, Pest. Sci. 35, 109, 1992. Copyright, Society of Chemical Industry with permission granted by John Wiley Sons, Ltd. on behalf of the SCI.]...

Once the process or design variables have been identified, a statistically designed experiment should be employed to collect appropriate data to fit the model. This plan includes developing the experimental objective, design matrix, and sample size (i.e., number of experimental replicates). 

The sporadic failure of leukocyte cultures or occasional low mitotic rates in long-term stationary tissue cultures necessitates experimental replication, preferably on different days. Ideally, all concentrations and exposure times of the agent should be repeated in each experiment. In addition to replicate cultures for each experiment, replicate cytological observations are also important to eliminate possible sampling errors. To this end, multiple slides should be made from each culture and examined on different days. To overcome possible observer bias, the same cells should be evaluated by more than one investigator and the results compared. Such a system would allow comparisons of precision to be made by a single observer at different times as well as by two different observers. 

Label-free quantification is a very attractive method, because there are no extra costs involved. Instead, there are much higher demands on the reproducibility of technical parameters, such as sample loading, chromatography, and mass accuracy, and more experimental replicates are needed. In the following sections, different approaches to label-free quantification will be discussed the extracted ion chromatogram (XIC), spectral counting (SC), the protein abundance index (PAI), and the LCMS method. 

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