Technical Notes

Indicators based on National Population Health Survey and the National Longitudinal Survey of Children and Youth (STC)

National Population Health Survey

The National Population Health Survey (NPHS), which began in 1994/95, collects information about the health of the Canadian population every two years. It covers household and institutional residents in all provinces and territories, except persons living on Indian reserves, Canadian Forces bases, and in some remote areas. The NPHS has both a longitudinal and a cross-sectional component. Respondents who are part of the longitudinal component will be followed for up to 20 years.

The Health Indicators data are based on both the longitudinal and cross-sectional components for household residents (institutional excluded) living in the provinces (territories excluded). Data are available for the first three cycles (1994/95, 1996/97 and 1998/99).

The 1994/95 and 1996/97 cross-sectional samples are made up of longitudinal respondents and their household members and individuals who were selected as part of supplemental samples, or "buy-ins", in some provinces. The 1998/99 cross-sectional sample is made up mostly of longitudinal respondents and their cohabitants. No buy-ins were added to 1998/99 data. However, to keep the sample representative, infants born in 1995 and thereafter and immigrants who entered Canada since the beginning of 1995 were randomly selected and added to the NPHS sample.

The 1994/95 provincial, non-institutional cross-sectional sample consisted of 27,263 households, of which 88.7% agreed to participate in the survey. After application of a screening rule to maintain the representativeness of the sample, 20,725 households remained in scope. In 18,342 of these households, the selected person was aged 12 or older. Their response rate to the in-depth health questions was 96.1% or 17,626 respondents. In 1996/97, the overall response rate at the household level was 82.6%. The response rate for the randomly selected individuals aged 2 or older in these households was 95.6%. In 1998/99, the overall response rate was 88.2% at the household level. The response rate for the randomly selected respondents 0 or older in these households was 98.5%.

The 1994/95 provincial, non-institutional longitudinal sample consisted of 17,276 respondents. A response rate of 93.6% was achieved in 1996/97, and a response rate of 88.9% was achieved in 1998/99.

When a sample size is too small, estimates become unreliable. Thus, some data are suppressed because of poor data quality. The threshold used to determine releasability of data is known as a release cutoff. When the number of respondents (weighted) falls below the marginal cutoff value, the data becomes suppressed. See Appendix 3 for release cutoffs for provincial and Canada cross-sectional data.

National Longitudinal Survey on Children and Youth

The National Longitudinal Survey of Children and Youth (NLSCY), developed jointly by Human Resources Development Canada and Statistics Canada, is a comprehensive survey which follows the development of children in Canada and paints a picture of their lives. The survey monitors children's development and measures the incidence of various factors that influence their development, both positively and negatively.

The first cycle of the NLSCY, conducted in late 1994 and early 1995, interviewed parents of approximately 23,000 children up to the age of 11. They shared information not only about their children, but also about themselves and the children's families, schools and neighbourhoods.

The second cycle, carried out in winter and spring of 1996-97, interviewed parents of the same children and provides unique insights into the evolution of children and their family environments over a two-year period. A new sample of newborn and 1-year-old children was added to cycle 2 to allow for cross-sectional estimates.

Collection of cycle 3 began in the fall of 1998 and was carried until June 1999. In addition to the original sample of children, who were aged 2 to 13 years at the time of the second data collection, a new sample of newborn and 1-year-old children was added to cycle 3 to allow for cross-sectional estimates. An extra cross-sectional sample of children 5 years old was also added to allow some provincial estimates for that age group.

Like the NPHS, small sample sizes in the NLSCY produce unreliable estimates. As such, unreliable data are considered to be of poor data quality and have been suppressed. Release cutoffs for the NLSCY are found in Appendix 3. All NLSCY data in Health Indicators are based on the cross-sectional files.

NOTE: The Highlights provided in this Issue are only meant to be general summaries of NPHS and NLSCY data. The proportions have not been tested for statistical significance, so readers should interpret the text with this in mind. Highlights in future issues of Health Indicators will take into account statistically significant differences in the estimates and proportions.