Those individuals who take part in Natsal may not be representative of the general population of Britain for two reasons. Firstly because in Natsal only one person per household is interviewed, this means that too high a proportion of Natsal participants will live in smaller household units. Secondly people from particular regions, different age-groups, men or women, may be more or less likely to agree to be interviewed than others, which we can establish by comparing our sample to official population estimates for Britain. Both of these problems however can be addressed by weighting the data, i.e. giving more importance to data from some participants than others. This ensures that, after weighting, our sample is representative of Britain, in terms of household size and also according to region, age and sex.