A statistical method for combining numerical data from more than one source into a single value. Each value from a given source is usually multiplied by a factor (its “weight”) which has been judged by the person producing the statistic to represent the importance of that factor in relation to the importance of the other factors going into the single final value. A simple example of the importance of weighting is found when it is necessary to “average averages” (it is usually stated that “you must NOT average averages”). For example, if a group of people was made up of 100 women with average height of 5 feet and 200 men with average height of 6 feet, it would be incorrect to simply add the two averages and divide by 2 (since there are two values going into the total): 5+6/2=5.5 feet (5’6″). “The correct method is one of weighting: 5×100 + 6×200 = 1200. Then 1200 is divided by 300 (total persons). The weighted average is 5.66 feet (5’8).
In radiation therapy that uses two opposing fields, the use of a higher dose for one of the fields.