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===Continuous===
===Continuous===
Continuous data can take any of a range of values, which can only be estimated to some degree of accuracy (for example, by increasing the accuracy, the value obtained will change). As such, the possible number of different values which the data can take are infinite. Examples of types of continuous data are weight, height, volume of milk produced during a lactation, and the infectious period of a pathogen. Age may be classified as either discrete (as it is commonly measured in whole years) or continuous (as the concept of a fraction of a year is plausible) - of these, the latter is probably more appropriate. Of course, age could alternatively be categorised and treated as ordinal data.
Continuous data can take any of a range of values, which can only be estimated to some degree of accuracy (for example, by increasing the accuracy, the value obtained will change). As such, the possible number of different values which the data can take are infinite. Examples of types of continuous data are weight, height, volume of milk produced during a lactation, and the infectious period of a pathogen. Age may be classified as either discrete (as it is commonly measured in whole years) or continuous (as the concept of a fraction of a year is plausible) - of these, the latter is probably more appropriate. Of course, age could alternatively be categorised and treated as ordinal data. Continuous data can be further categorised according to the
====Interval====
====Interval====
Interval data do not possess what is known as '''relationship of scale''', due to the presence of an arbitrarily-defined zero point. This means that although (as for all quantitative data), an ''absolute'' difference of a set magnitude is the same regardless of where on the scale of measurement this difference is, the same does not apply to ''relative'' differences. Interval data can also take negative values. To explain this, consider the celsius temperature scale: although the absolute difference of 10°C between 10°C and 20°C is the same as that between 90°C and 100°C, the relative difference in temperature between 10°C and 20°C is very different from that between 50°C and 100°C. As such, it would be incorrect to classify either of these relative differences as a difference of '100%'.
====Ratio====
====Ratio====
Ratio data do possess a relationship of scale, and so both have a defined zero point and cannot accommodate negative values. Many common types of measurements are on the ratio scale - including mass, length and time. Temperature is also measured on the ratio scale when measured in Kelvin rather than Celsius or Fahrenheit (note that in the case of the difference between Kelvin and Celsius, the sole difference in measurement scale relates to the position of the zero point, since both scales have the same magnitude).
[[Category:Veterinary Epidemiology - Introduction|B]]
[[Category:Veterinary Epidemiology - Introduction|B]]