Presentation on theme: "Chuck Humphrey Data Library University of Alberta."— Presentation transcript:
Chuck Humphrey Data Library University of Alberta
Quantitative evidence Distinction between statistics and data Observational evidence Statistics are about definitions and classifications Aggregate data and microdata Understanding the Census Access to evidence Statistical and aggregate data sources Microdata sources
Statistics numeric facts & figures derived from data, i.e, already processed presentation-ready need definitions published Data numeric files created and organized for analysis/ processing requires processing not display-ready need detailed documentation disseminated, not published
Six dimensions or variables in this table The cells in the table are the number of estimated smokers. Geography Region Time Periods Social Content Smokers Education Age Sex
The National Population Health Survey in the previous example had over 80,000 respondents in 1996-97 sample and the Canadian Community Health Survey in 2005 has over 130,000 cases. How do we tell the stories about each of these respondents? We use statistics to create summaries of these life experiences. Data enable us to construct the tables or analyses to tell these summarized stories.
Statistics are dependent on definitions. You may think of statistics as numbers, but the numbers represent measurements or observations based on specific definitions.definitions Tables are structured around geography, time and social content based on attributes of the unit of observation. These properties all need definitions.
Classifications Sex Total Male Female Periods 1994-1995 1996-1997
Some classifications are based on standards while others are based on convention or practice. For example, Standard Geography classifications Geography classifications
It is helpful to understand some basics about the origins of data, especially since statistics are derived from data. As we will see later, having a good understanding of data can greatly help in the search for statistics. There are three generic methods by which data are produced. Statistics are generated from the data produced out of all of these methods. Observational Methods Experimental Methods Computational Methods
Observational Methods Experimental Methods Computational Methods Focus is on developing observational instruments to collect data Focus is on manipulating causal agents to measure change in a response agent Focus is on modeling phenomena through mathematical equations CorrelationCausationPrediction Replicate the analysis (same data or similar) Replicate the experiment Replicate the simulation Statistics summarize observations Statistics summarize experiment results Statistics summarize simulation results
Statistics are derived from observational, experimental and simulated data. A table is a format for displaying statistics and presents a summary or one view of the data. Tables are structured around geography, time and attributes of the unit of observation. Statistics are dependent on definitions. Working with data requires some computing skills with analytic software.
Who published this statistic? Can you name the producer or distributor of the data? You need this information to provide a citation for each statistic. You should ask yourself what motive is behind this published statistic. What view of the data is shown in this statistic? What level of geography is shown? What time period is shown? What social characteristics are shown?
What concepts are represented in this statistic? Are definitions provided with the statistic for geography, time or the social characteristics? Was a standard classification system used for the categories of the statistic? Can you identify a data source for the statistic? If there isn’t a data source, the statistic isn’t real. Is there enough information that you could find the data? Can you name the data source itself?
The Census is the largest survey collected in Canada and is taken every five years. The last two censuses were in 2001 and 2006. The censuses in years ending in 1 are known as the decennial census and contain certain questions only asked every ten years (e.g., religion.)
Two forms are used to collect the Census: 2A, which goes to 80% of the households, and 2B, which goes to the other 20%. In 2006, the 2A form contained 8 questions while the 2B form had these 8 and 53 additional questions. Long history of specific questions (see the Census Dictionary.)history of specific questions Need to understand the content of the Census to know what statistics are possible from the Census.
The Census Dictionary is also important to understand the current definitions for concepts as well as historical definitions.Census Dictionary Here is an example on aboriginal identity: “The Aboriginal identity question was asked for the first time in the 1996 Census. It asked the respondent if he/she was an Aboriginal person, i.e., North American Indian, Métis or Inuit. The question is used to provide counts of persons who identify themselves as Aboriginal persons. The concept of 'Aboriginal identity' was first used in the 1991 Aboriginal Peoples Survey.”
The unit analysis makes up the rows in the data file and is the object being described by the other variables the file. The values for this variable are geo-codes for Census tracts.
This case in the data file represents Census Tract 0023.00, which was shown in the image two slides earlier.
Statistics Canada groups the variety of geographic units associated with the Census into two categories: Source for the graphics: Illustrated Glossary, 2006 Census Geography, Statistics Canada Source: Illustrated Glossary, 2006 Census Geography, Statistics Canada
Statistics Canada has two categories of geo-code systems: Standard Geographic Classification (SGC) Other geographic entities Source for the graphic: Illustrated Glossary, 2006 Census Geography, Statistics Canada
Source: Illustrated Glossary, 2006 Census Geography, Statistics Canada
The link to Definitions, data sources and methods on the main page of the Statistics Canada website provides a link to Standard Classifications, which includes Geography. Definitions, data sources and methods Geography
Census Metropolitan Areas Source for the graphic: Illustrated Glossary, 2006 Census Geography, Statistics Canada Metropolitan Areas 2006Map of Edmonton CMA
For characteristics about Canadians, you need to become familiar with Statistics Canada’s website.website This is a complex website. Use the “Popular picks” list on the home page and search for statistics by browsing subject terms. Historical Statistics Historical Statistics
E-STAT is a portal to free CANSIM time series statistics and Census results from 1981 to 2006. E-STAT CANSIM on Statistics Canada’s website charges $3.00 a time series, while these statistics accessed through CANSIM on E- STAT are free.
The Library homepage has useful guides for locating statistics online and in printguides
Microdata from observational methods created from the respondents in a survey Aggregate Data statistics organized in a data file structure derived from microdata sources used in GIS & time series analysis