What exactly is ‘N’ in cell culture and animal experiments?
Fig 2
An EU can correspond to a BU of interest such as an animal (A); groups of BUs, when they are randomised by group or when the treatment is applied group-wise (B); or parts of a BU, where each animal forms the ‘recognisable subgroup’ (C). A less common example is when an experiment is divided into time periods that are randomly assigned to different treatment conditions and a measurement is taken during each time period. Note how the number of animals may differ from the sample size (N). The 2 experimental conditions are represented with syringes (white = control, black = treated). Adapted from Lazic [21]. BU, biological unit; EU, experimental unit.
doi: https://doi.org/10.1371/journal.pbio.2005282.g002