Sentence:  Note that (1.41) is simply the probability-weighted <WSD>mean</WSD> without any explicit allowance for the stratification; each observation is weighted by its inflation factor and the total divided by the total of the inflation factors for the survey. 
Meaning of the word marked with <WSD> tags:  Any function of multiple variables that satisfies certain properties and yields a number representative of its arguments; or, the number so yielded; a measure of central tendency.