tagged: replicates

Technical Replicates

Posted by ludesi in 2DE Knowledge Base

Andreas Ekefjard, CTO and Biostatistician at Ludesi, answers:

Q: “How many technical replicates should I use in my experiments?”

A: By technical replicates we mean two or more gel images that have been produced from the same sample material. Independent samples on the other hand have no connection to any of the other samples, and can thus be thought of as having been sampled from a much larger population.

The purpose of using technical replicates

If the main concern is to maximize statistical power, it is best to include as many independent samples as possible rather than technical replicates.

If however you only have access to a limited number of independent samples, you can run technical replicates in order to “average out” the technical variation. This is of course provided you have enough sample material to run replicates.

Another common reason to run technical replicates is to gain information on the technical variation in your setup. By running the same sample several times, you can distinguish the level of variation that is present in the absence of sample variation.

Statistical treatment

Note that to be able to perform common statistical test such as t-test / ANOVA, it is necessary that at least one of the groups contain more than one independent sample. (In order to achieve a reasonable power however, you realistically need many samples per group.)

Several technical replicate gel images from the same sample naturally still count as one single independent sample. If technical replicates are present, the ANOVA will use average protein spot volumes calculated from all replicates made from the same sample. In this fashion, the presence of technical replicates will reduce the influence of technical variation.

Nonetheless, for an equal number of gel images, independent samples are preferable to technical replicates for the purpose of maximizing statistical power.