The Imperial versus Metric Study (IMS)

Collaborating Institutions: 

BEAR Center Participants: 
Mark Wilson, Yiyu Xie


The Imperial versus Metric Study (IMS) carried out jointly by BEAR and WESTAT is part of a larger study, namely PISA (Programme for International Student Assessment). PISA was coordinated by governments of participating countries, through the Organisation for Economic Co-operation and Development (OECD). A survey of the knowledge and skills of 15-year-olds in the principal industrialized countries was first conducted in 2000, and will be repeated every three years. PISA assesses literacy in reading, mathematics and science. (For more info, check out the PISA website).


The overall purpose of the IMS is to examine whether there is any support for the speculation that US students might be relatively disadvantaged in international comparisons of achievement by the use of metric units (e.g., meters, liters, etc.) in items rather than the more familiar (to US students) imperial units (e.g., feet, gallons, etc.). The PISA 2003 main study has a focus on mathematics, therefore, matching imperial versions of math items containing metric units have been made. Data will be collected on both imperial and metric samples from the US participants. Psychometric analysis using differential item functioning (DIF) will be conducted.