Salah Merad and Heather Wagstaff Office for National Statistics, UK Survey Methods Division

1. A Management Information System for Controlling Editing Quality in a Survey with Multiple Requirements Salah Merad and Heather Wagstaff Office for National Statistics, UK Survey Methods Division

2. Outline • Problem • Solution

3. Problem • Surveys where selective editing is applied to several variables • Threshold values can be specific to sub-groups of variables • Difficult to estimate accurately editing resource • Number of failures variable • Changes to questions, new questions • Need to know at run time whether available resource is likely to be outrun by the amount of failures • Take action to concentrate on most significant errors: raise thresholds by an appropriate amount

4. Solution • Editing process monitored at regular intervals • Error rates computed for main error types (selective editing errors, other errors) • Decision rule • Compares the available editing time with the time required to complete the expected workload given available information • Need to estimate number of future failures • Need estimates of average processing time for different error types • Indicates by how much to reduce number of failures, if necessary

5. Solution • Several thresholds to be determined simultaneously • Thresholds need to be robust • Solve the optimisation problem: • Minimise distance between original thresholds and new thresholds Subject to: • Number of selective editing failures reduced by a specified amount • Thresholds do not exceed specified safety bounds • Problem solved using a heuristic based on hill climbing: use data available up to current time