Data quality, concepts and methodology: Data Sources

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General Social Survey

Sampling

In 2009, Statistics Canada conducted the victimization cycle of the General Social Survey (GSS) for the fifth time. Previous cycles were conducted in 1988, 1993, 1999 and 2004. The objectives of the survey are to provide estimates of Canadians' personal experiences of eight offence types, examine risk factors associated with victimization, examine reporting rates to police, measure the nature and extent of spousal violence, measure fear of crime and examine public perceptions of crime and the criminal justice system.

The target population included all persons 15 years and older in the 10 Canadian provinces, excluding full-time residents of institutions, such as hospitals or prisons. The survey was also conducted in the three Canadian territories using a different sampling design and its results will be available in a separate report to be released in 2011. Households were selected by a telephone sampling method called Random Digit Dialling (RDD). Once a household was contacted an individual 15 years or older was randomly selected to respond to the survey. Households without telephones or those with only cellular phone service were excluded from the survey. These two groups represented approximately 9% of the target population in 2009 and 4% in 2004. The coverage, therefore, for 2009 (Cycle 23) and 2004 (Cycle 18), was 91% and 96%, respectively.

Data collection

Data collection took place from February to November 2009 inclusively. The sample was evenly distributed over the 10 months to represent seasonal variation in the information. A standard questionnaire was administered by phone using computer-assisted telephone interviewing (CATI). A typical interview lasted 45 minutes.

Response rates

Of the 31,510 households that were selected for the GSS Cycle 23 sample, 19,422 usable responses were obtained. This represents a response rate of 61.6%, a decrease from 2004 (74.5%). Types of non-response included respondents who refused to participate, could not be reached, or could not speak English or French. Respondents in the sample were weighted so that their responses represent the non-institutionalized Canadian population aged 15 years or over. Each person who responded to the 2009 GSS represented roughly 1,400 people in the Canadian population aged 15 years and over.

Data limitations

As with any household survey, there are some data limitations. The results are based on a sample and are therefore subject to sampling error. Somewhat different results might have been obtained if the entire population had been surveyed. This report uses the coefficient of variation (CV) as a measure of the sampling error. Any estimate that has a high CV (over 33.3%) has not been published because the estimate is too unreliable. In these cases, the symbol 'F' is used in place of an estimate in the charts and data tables. An estimate that has a CV between 16.6 and 33.3 should be used with caution and the symbol 'E' is referenced with the estimate. Where descriptive statistics and cross-tabular analysis were used, statistically significant differences were determined using 95% confidence intervals.

Using the 2009 GSS sample design and sample size, an estimate of a given proportion of the total population, expressed as a percentage, is expected to be within 0.95 percentage points of the true proportion 19 times out of 20.

Incident-based Uniform Crime Reporting Survey

The Incident-based Uniform Crime Reporting (UCR2) Survey collects detailed information on criminal incidents that have come to the attention of, and have been substantiated by, Canadian police services. Information includes characteristics pertaining to incidents (weapon, location), victims (age, sex, accused-victim relationship), and accused persons (age, sex). In 2009, data from police services covered 99% of the population of Canada.

Homicide Survey

The Homicide Survey collects detailed information on all homicides that have come to the attention of, and have been substantiated by, Canadian police services. Information includes characteristics pertaining to incidents (weapon, location), victims (age, sex, accused-victim relationship), and accused persons (age, sex). Coverage for the Homicide Survey has represented 100% of the population since recording began in 1961. The count for a particular year represents all homicides reported in that year, regardless of when the death actually occurred.

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