Although care has been taken to ensure the results of the 2010 GSS are as accurate as possible, all sample surveys are subject to error which can be broadly categorised as either sampling error or non-sampling error. Sampling error occurs because only a small proportion of the total population is used to produce estimates that represent the whole population. Sampling error can be reliably measured as it is calculated based on the scientific methods used to design surveys. Non-sampling errors occur when survey processes work less effectively than intended. For example, some persons selected for the survey may not respond (non-response); some survey questions may not be clearly understood by the respondent; and occasionally errors can be made in processing data from the survey. Sampling and non-sampling errors should be considered when interpreting results of the survey.