The use of ratios in epidemiology is different than the uses of portions and rates. In today’s epidemiology ratios are defined as the value obtained by dividing one quantity by another. This can be seen if one was to compare the number of motorcycle fatalities of men to female. So if 950 males died in a motorcycle and only 50 female the ratio would equate to 19:1 males to females. While a proportion is also a ratio where the numerator is part of the denominator commonly expressed as a percentage. A way to understand a portion is to say 5 children in a class contracted chicken pox. So this classroom contains 25 kids, making 20% of the kids sick in the class. Lastly, we have rates that are different than both ratios and portions. While a rate
