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====Means====
====Means====
As described [[Data description|earlier]], means are the most appropriate measure of central tendency for normally distributed continuous variables, and the '''standard deviation''' is the most appropriate measure of 'spread' in these cases. An adjusted form of the '''sample standard deviation''' is used to approximate the standard deviation in the population, and is calculated by dividing the sum of the squared differences from the sample mean by the number of animals sampled minus 1, and taking the square root of the answer.
As described [[Data description|earlier]], means are the most appropriate measure of central tendency for normally distributed continuous variables, and the standard deviation is the most appropriate measure of 'spread' in these cases. An adjusted form of the sample standard deviation is used to approximate the standard deviation in the population, and is calculated by dividing the sum of the squared differences from the sample mean by the number of animals sampled minus 1, and taking the square root of the answer.
====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 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 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.
===Approach for rates and ratios===
===Approach for rates and ratios===
Although the general concept behind confidence intervals for rates and ratios is the same as that for means and proportions, the method of calculation is different.
[[Category:Veterinary Epidemiology - Statistical Methods|D]]
[[Category:Veterinary Epidemiology - Statistical Methods|D]]