Response rate How do you calculate the response rate? –What is target population? –Enable standardisation/comparison across studies –Requires assumptions about eligibility (deaths etc) –Moving in and out of sample (response rate at each sweep) –Guidelines on target sample & education of journals/editors – TRENDS statement? –Importance of reporting response rates and characteristics of attrittors –Problems with response rates for cluster samples

Achieving high response rates Cost effectiveness of high response –Comparable cost data on expenditure of reducing attrition from cohorts –Rational allocation of resources (not tracing refusers) –Attrition in hard to reach groups introducing bias –‘true responders’ in long term follow-up Too much interaction with subjects biasing data quality –Refusal conversion –Maintaining objectiveness of data collection

Achieving high response rates Using substudies & implications for response rates Papers devoted to attrition in studies Study design including investigation of attrition (including questions) Ethics of refusal conversion?