Number raised estimation refers to the application of weights to the individual survey records. Number-raised weight's are given by N/n (where N is the total number of units in the population for the stratum, and n is the number of responding units in the sample for that stratum).
The weight assigned to each survey unit indicates the number of units in the target population that the survey unit is meant to represent. For example, a survey unit with a weight of 100 represents 100 units in the population. Using number-raised weights, each survey unit in a stratum is given the same weight. Number-raised weights can only be used with simple random samples.