Error

There are different types of errors in surveys : coverage error (the sampling base does not correspond exactly to the population studied), non-response error (a part of the sample does not wish to answer certain questions), measurement error (the value declared by the individual is incorrect) and sampling error (only a part of the population is observed). The combination of these errors - the total error - is the difference between the survey-estimated value and the (generally unknown) “true value” of the parameter in the population.