Phase-in of Computer Assisted Interviewing to the Labour Force Survey
Prior to 2003, Labour Force Survey (LFS) interviewers have made use of paper forms to collect information from respondents. The ABS is in the process of phasing-in the use of Computer Assisted Interviewing (CAI) for the LFS between October 2003 and June 2004. In October 2003, 10% of interviewers made use of computers for the first time (i.e. about 6,000 persons or interviews). The remaining interviewers will be phased-in from paper forms to CAI over 2004.
A delay between the first and second phase-in groups was designed to minimise risks associated with the computing systems: if there were system problems associated with the 10% sample in October, then there would be 3 months to fix them before the next, much larger, phase-in of interviewers scheduled for February. Also, the first phase-in group was small in size in order to mitigate the risk of a substantial mode effect. In such a situation, dropping the CAI sample (10%) of respondents would only have a minor affect on the coherence of the LFS time series. Lastly, the period of the phase-in was limited in order to minimise the period of uncertainty affecting the LFS series.
Given the small size of the first phase-in group, it was accepted that a statistical test for a mode effect would have poor accuracy and low power.
Household Survey Methodology's (HSM) involvement in this project has been to:
Composite estimation is being used to assess the mode effect. A composite estimator makes use of more than one month of LFS data. In this case, to estimate a potential mode effect in the October LFS estimates, the composite estimator makes use of August, September and October LFS data.
Investigations into the existence of a possible mode effect are continuing. Four months of data have been analysed so far, but the results of these investigations are less than definitive given the size of the sample. Further analysis following the phase-in of the second group is expected to be more conclusive.
For more information, please contact James Chipperfield (02) 6252 7301.
- randomly select interviewers to one of the phase in groups;
- maintain a frame of interviewers in order to make these selections;
- ensure that the selected interviewers in each group are allocated a representative sample of workloads, in terms of location and the LF status of the persons interviewed;
- measure the size of the mode effect at various levels (Australia, state, part of state), by characteristics of the respondents (age and sex), characteristics of the interviewer (experience of interviewer) and characteristics of the interview (whether the interview took place face-to-face or over the telephone);
- isolate potential sources of the mode affect, in order to inform users, and to determine if the mode effect is a phantom affect (i.e. due to non-CAI sources).