Changes

====Proportions====

====Proportions====

Proportions are the most appropriate method of description of [[Data description|categorical and binary]] variables. Although the concept of a 'variance' or 'standard deviation' for these samples is difficult to comprehend, the 'standard deviation' of a binary variable can be calculated by multiplying the proportion of positive animals by the proportion of negative animals, and by taking the square root of this.

Proportions are the most appropriate method of description of [[Data description|categorical and binary]] variables. Although the concept of a 'variance' or 'standard deviation' for a proportion is difficult to comprehend, it is based upon the 'binomial distribution'. The variance can be estimated by multiplying the proportion of positive animals by the proportion of negative animals; and the square root of this will give the standard deviation.

===Approach for rates and ratios===

===Approach for rates and ratios===