Note to Readers

The skill proficiency results from the ALL study are reported separately for four scales – prose literacy, document literacy, numeracy, and problem solving – rather than on a single scale. Although it is desirable to maintain separate scales for the majority of more complex analyses, the theoretical and empirical properties also allow for creating composite skill scales. The prose and document literacy scales are combined into a composite literacy scale for some analyses in this book.

Multiple sources of uncertainty and error are a fact of life in social science research. Given the comparative nature of the ALL study, those responsible for the design of the study and its implementation went to great lengths to establish the validity, reliability, comparability and interpretability of estimates, and to control and quantify errors that might interfere with or bias interpretation. Statistics Canada, the Educational Testing Service and the national study teams have performed comprehensive analyses to understand the nature and extent of errors associated with subtle differences in design and implementation. Notes to figures and tables are used to alert readers whenever errors have been detected that might affect interpretation.

The data values presented in this volume are estimated from representative but complex samples of adults from each country. Consequently there is a degree of sampling error that must be taken into account. Additionally, there is a degree of error associated with the measurement of skills because they are estimated on the basis of responses to samples of test items. Thus a statistic, called the standard error, is used to express the degree of uncertainty associated with both sampling and measurement error.