Data limitations

It is worth noting that the figures appearing in this publication are estimates based on data collected from a small fraction of the population (roughly one person in 1,800) and are subject to error. There are two types of errors: sampling errors and non-sampling errors.

Sampling error is the difference between an estimate derived from the sample and the one that would have been obtained from a census using the same data collection methods for the entire population. The size of the sampling error can be estimated from the survey results and an indication of the magnitude of this error is given for the estimates in this report. If the estimated sampling error is greater than 33% of the estimate, it is considered too unreliable to publish and the symbol "F" is printed in table cells where this occurs. Although not considered too unreliable to publish, estimates with an estimated error between 16.6% and 33.3% are marked "qualified" and used with caution. These are identified with an "E".

All other types of errors, such as coverage, response, processing and non-response errors, are non-sampling errors. It is difficult to identify and evaluate the scope of many of these errors.

Coverage errors arise when there are differences between the target population and the surveyed population. Households without a telephone represent part of the target population that was excluded from the surveyed population. To the extent that this excluded population differs from the rest of the target population, the estimates will be biased. Since these exclusions are infrequent, one would expect the introduced biases to be small. However, since there are correlations between a number of questions asked on this survey and the groups excluded, the biases may be more significant than the small size of the groups would suggest.

Similarly, to the extent that the non-responding households and persons differ from the rest of the sample, the estimates will be biased. Non-response could occur at several stages in this survey. There are two stages of data collection: collection at the household level and at the individual level. As such, some non-response occurred at both levels. Non-response also occurred at the level of individual questions.

For most questions, the response rate was high, with non-response indicated in the data files. While refusal to answer specific questions was very low, accuracy of recall and the ability to answer certain questions completely can be expected to affect some of the results presented. The criteria for accepting a time use diary were stringent, requiring respondents to report at least 20 out of 24 hours of activities. Time use episodes for which activity details were not stated are shown as "residual time".

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