IEA Civic Education Study. Technical Report. Amsterdam - ACER

Together with the data files, the documentation provided by the nationalcenters was reviewed. On the basis of the initial checks, the IEA DPC outlinedand implemented the changes necessary to standardize the file structure.CLEANING RULES AND PROCEDURESAfter the transformation of national data into the international file structure,standard cleaning routines were applied to the data. In a first step, a diagnosticprogram detected possible problems in the data. During this step, the followinggroups of problems were under consideration:• valid ranges;• duplicate records;• flaws in the ID system;• participation status (from the tracking form) against data (from thequestionnaire);• participation status against exclusion status; and• inconsistencies in participants’ answers.All problems detected in this step were reported in an error database. In asecond step, routine programs were used to solve many of these errors. Most ofthem were due to the wrong usage of missing values. In a third step, remainingproblems were addressed by manual operation, which required thoroughreviews of tracking forms or further communication with the NRCs.When all automatic and manual changes had been applied to the data, thediagnostic program used in the first step was applied again, and the resultingerror database was compared to the previous error database. Ideally, at the endof this procedure, all problems should have been removed from the data.However, it sometimes happened that problems persisted or new problems werecreated in the data. The data cleaning steps then had to be repeated until noproblems remained.The review of file linkages between files was based on the information from allfiles involved in the study. Only records from participating respondents wereused in this final data-cleaning step. During NRC meetings, the NRCs receiveddetailed reports on database problems and the solutions applied to the data.DATA PRODUCTSData products sent by the IEA DPC to the ICC included both data files anddata summaries, depending on the needs of the ICC.Data summaries contained unweighted summary statistics for each participatingcountry on each variable in the survey instrument. The display for categoricalvariables, which represented the majority of variables in the data files, includedthe percentage of respondents choosing each of the options on the question,the percentage of respondents choosing none of the valid responses, and thepercentage of students to whom the question had not been administered. Thesesummaries were used for an in-depth review of the data. If, for example, noanswer was found in a particular response category, the corresponding questionas used in the country was scrutinized to detect possible printing errors. Table5.1 shows an example of a summary statistic.58 IEA CIVIC EDUCATION STUDY TECHNICAL REPORT