3.2.2. Zero values

Since it is not possible to log-transform zero values, instances of non-detection (i.e. a ‘zero’ value) should be replaced by a non-zero constant value appropriate to the variable in question (Cox et al., 2000). A logical constant value to use for replacing zero-values in quantitative virus data sets is one that is set just below the detection threshold for the virus in question (Yañez et al., 2012; Locke et al., 2012). This approach treats zero values as “below detection threshold” rather than as “absence of virus”, which is usually also a more accurate description of the virus status of a sample, especially if the virus is known to be present within the wider bee population.