1. Sleeping is ATUS activity code 010101, and Grooming is 010201. Travel time included. Standard errors in parentheses, 90-percent confidence intervals in brackets;USDA, Economic Research Service using data from 2006-08 American Time Use Survey (ATUS) and Eating and Health Module
2. How Social Processes Distort Measurement: The Impact of Survey Nonresponse on Estimates of Volunteer Work in the United States;Katharine G Abraham;NBER Working Paper Series,2008
3. Nonresponse in the American Time Use Survey: Who Is Missing From the Data and How Much Does It Matter?;Katharine G Abraham;Public Opinion Quarterly,2006
4. A Review of Hot Deck Imputation for Survey Non-response;R R Andridge;International Statistical Review,2010
5. Handbook of Nonresponse in Household Surveys