BIOS 1500 Lecture Notes - Lecture 6: Cumulative Incidence, Foodborne Illness, Prevalence
Document Summary
There can often be misunderstandings and misuse of terms regarding rates, ratios and proportions. The misunderstandings were so great or annoying to statisticians that at least one paper was written on this topic: elandt-johnson (1975) am. Even with this paper and a lot of ranting and raving the situation has not changed. A ratio is the result of dividing one quantity by another. Specifically if a and b are two numbers, then the ratio of a to b is. A ratio is the most generic or primitive of the three indices, and is sometimes written a:b. Consider the sex ratio of males to females. Sex ratio = number of males /number of females. Fetal death ratio is the number of fetal deaths divided by the number of live births. Bmi is a ratio of two scale variables: weight in kg and height in meters: (cid:1835)=(cid:1834)2. Ratios can be applied to both interval and ratio data values.
