SOCIOECONOMIC CONTEXT OF STUDENT ACHIEVEMENT (EXPLANATORY NOTES)
DATA SOURCES
1 This publication uses school enrolments data for Tasmania for 2006 to 2013, National Assessment Program – Literacy and Numeracy (NAPLAN) data for Tasmania from 2008 to 2013 and data from the 2011 Census of Population and Housing (the Census).
School Enrolments data
2 The school enrolment data used in this publication was collected by the Tasmanian Department of Education. The statistics are compiled from student level data, excluding name and address, for each child enrolled in a government school in Tasmania at any time between 2006 and 2013 inclusive. This dataset contained records for 142,816 students.
National Assessment Program – Literacy and Numeracy
3 NAPLAN is a skills test that provides nationally comparable data on the literacy and numeracy performance of students at the time of the test. Each year, all students in Years 3, 5, 7, and 9 participate in tests covering reading, writing, language conventions and numeracy. The Australian Curriculum Assessment and Reporting Authority (ACARA) manages the development of, and oversees the delivery of tests for NAPLAN. Administration of the tests, including marking, is managed by the Test Administration Authority in each state or territory.
4 This publication uses NAPLAN results in Tasmania for the years 2008 to 2013. The statistics are compiled from student unit record level data, excluding name and address, for each child participating in the tests in government schools in Tasmania. The NAPLAN data utilised in this study were provided to the ABS by the Tasmanian Department of Education, the Test Administration Authority for Tasmania. This dataset contained records for 58,869 students.
Census of Population and Housing
5 The Census is undertaken by the Australian Bureau of Statistics every five years, and is collected under the authority of the Census and Statistics Act 1905. For information about the 2011 Census please refer to the information provided on the Census 2011 Reference and Information section of the ABS website. Information about the data quality of the Census is also available on the ABS website under Census Data Quality.
SCOPE
6 The scope of the first phase of the Measuring Education Outcomes over the Life-course project utilising a Tasmanian school enrolments, NAPLAN and Census integrated dataset is restricted to people who responded to the 2011 Census of Population and Housing and had a Tasmanian government school enrolment record in 2006 to 2013.
DATA INTEGRATION
7 Statistical data integration involves combining information from different administrative and/or survey sources to provide new datasets for statistical and research purposes. Further information on data integration is available on the National Statistical Service website – Data Integration.
8 Data linking is a key part of statistical data integration and involves the technical process of combining records from different source datasets using variables that are shared between the sources. Data linkage is typically performed on records that represent individual persons, rather than aggregates. The most common methods link records on exact matches for common variables ('deterministic' linkage), or close matches ranked by probabilities that the variables used will result in a true match ('probabilistic' linkage).
Creating a longitudinal school enrolments and NAPLAN dataset
9 The creation of a longitudinal school enrolments and NAPLAN dataset was carried out using the Student ID.
10 The Student ID is a unique identifier assigned to each individual student enrolled in the Tasmanian government school education system, from pre-year 1 to senior secondary. The Tasmanian Department of Education collects school enrolment data via the Government Schools Administrative Computer System, which involves extensive validation and quality assurance checks on the data submitted from each school. The same Student ID is available on both the school enrolments and NAPLAN datasets for Tasmania.
11 Each Student ID is unique to a single student and therefore if two exact matches of a Student ID are found within the school enrolments dataset for a given year, this would indicate that the student has multiple enrolments within a year.
12 A student enrolled in more than one Tasmanian government school at the same time (e.g. a student that attends one of their classes at a different school) would have the same Student ID recorded for both enrolments. A small number of records were removed from the dataset due to apparent data inconsistencies that could not be resolved.
13 Records were linked using Student ID across the multiple years of school enrolment records and NAPLAN data. There were 152 records on the NAPLAN dataset that did not have a corresponding match on the school enrolments dataset, and so were not linked.
Linkage between the longitudinal school enrolments and NAPLAN dataset with Census data
14 The Tasmanian longitudinal school enrolments and NAPLAN dataset was linked to the 2011 Census of Population and Housing data using a deterministic linkage methodology that requires exact matches between variables common to both datasets. It is considered a "bronze" standard linkage because name and address information were not used in the linkage process. Data was linked using date of birth, sex, and codes representing small geographic areas. As the school enrolments data was for multiple years, data was linked to the Census using geographic codes representing place of usual residence, place of usual residence one year ago, and place of usual residence five of years ago.
15 Information about linkage methodologies used in similar studies can be found in Research Paper: Assessing the Quality of Linking School Enrolment Records to 2011 Census Data: Deterministic Linkage Methods (cat. no. 1351.0.55.045) and Research Paper: Assessing the Quality of Different Data Linking Methodologies Across Time, Using Tasmanian Government School Enrolment Data (cat. no. 1351.0.55.047).
Linkage results
16 At the completion of the linkage process, 99,962 (70%) out of the 142,732 remaining records from the school enrolments and NAPLAN dataset were linked to the 2011 Census data. Whilst the linkage rate is slightly lower than results from other Bronze linkage projects using the 2011 Census data, the overall linkage accuracy for this project was estimated to be very high, at 97%. This was deemed to be the most appropriate balance of linkage rate and linkage accuracy. There is potential to raise the linkage rate, however, any small increase in the linkage rate would be outweighed by the loss in link accuracy. As the focus of this project is to produce longitudinal estimates, including for sub-populations, linkage accuracy was treated as higher importance than a slight increase in the linkage rate.
17 While of a high quality, these links still have a small chance of being false. This chance of error is influenced by a few factors. The first factor is the amount of missing or invalid information for the linking variables used. Matches can only be made on valid responses and any of the unique links could have potentially been duplicated in the records with missing or invalid information if that information was present.
18 The second factor is persons on the school enrolments/NAPLAN data who were missing on the Census data. While both sources of data are population counts, students may not have filled in a Census form in 2011 because they were no longer a resident of Australia, were abroad temporarily at the time of collection, or were missed for another reason. Similarly to the first factor, these people who were missing from the 2011 Census could have created duplicate records for the links that were considered unique.
19 Another factor impacting on potential error is the quality of the variables used for linking. While inaccurate responses for variables have a small impact here, the larger impact comes from the efficacy of variables to match records uniquely out of a pool of possible links. Variables that have a large number of possible responses that are spread across records, such as date of birth, are more effective than variables with few responses and a less varied spread, such as sex.
WEIGHTING
20 Weighting is the process of adjusting a sample to infer results for the relevant population. The estimates in this publication are obtained by assigning a 'weight' to each linked record. The weight is a value which indicates how many students' records are represented by the linked record. Weights aim to adjust for the fact that the linked student records may not be representative of all the student records. Weighting was used to ensure better representation of population sub-groups and to enhance the reliability of linked education data for longitudinal and cross-sectional analysis.
21 Frequencies on demographic variables were run to analyse how representative the final linked dataset was of the longitudinal school enrolments and NAPLAN dataset to determine the most appropriate weighting strategy. Weights were then applied to the records in the final linked dataset in order to make the data representative of the school enrolments dataset, and to allow for estimates to be produced for the school enrolments/NAPLAN population rather than just the linked sample.
22 Weights were benchmarked to the following population groups:
▪ which years of enrolment records were available for that student (12 categories)
▪ SEIFA Index of Relative Socio-Economic Disadvantage (three categories)
▪ age group (ten categories).
23 The weights have a mean value of 1.43 and range between 1 and 16.
24 Of the 142,732 records from the longitudinal school enrolments and NAPLAN dataset, 58,717 records had a NAPLAN result. Of these, 48,317 were successfully linked to the Census data. While presence of a NAPLAN record was not explicitly accounted for in the weighting strategy, the weighted total of these records was 58,579, extremely close to the actual figure.
USE OF DATA
25 As the data in this publication is based on weighted estimates, there may be differences between figures in this publication and those published elsewhere.
26 While every effort was made to assure the quality of the statistics presented in this publication, they should be considered experimental and treated with caution.
27 Any discrepancies between totals and sums of components are due to rounding.
POPULATIONS
Socioeconomic context of student achievement in Tasmania
28 The Socioeconomic context of student achievement in Tasmania article uses all NAPLAN results in Tasmania for 2011 which were successfully linked to the 2011 Census. This represents a weighted total of 16,874 students with reading results, 16,930 for writing and 16,802 for numeracy. The breakdowns of students by grade level are outlined in the following table.
WEIGHTED NUMBER OF STUDENTS WITH NAPLAN RESULTS, BY GRADE(a)
|
 | Reading | Writing | Numeracy |
|
|
| Year 3 | 4,402 | 4,393 | 4,379 |
| Year 5 | 4,634 | 4,637 | 4,619 |
| Year 7 | 3,926 | 3,942 | 3,917 |
| Year 9 | 3,913 | 3,958 | 3,886 |
| Total | 16,874 | 16,930 | 16,802 |
|
| |
(a) For Socioeconomic context of student achievement in Tasmania article only.
Destinations and outcomes of Tasmanian early school leavers
29 The Destinations and outcomes of Tasmanian early school leavers article contains two cohorts. The majority of the article is based on a weighted cohort of 4,173 students who were enrolled in Year 9 in 2008 within a Tasmanian government school and had a NAPLAN reading score in that year.
30 A subset of this cohort which is examined in the article is students who left school before enrolling in Year 12. This group was identified by excluding anyone for whom we had a Tasmanian government Year 12 enrolment record in the years up to and including 2013, or whose Census record indicated that they were either attending secondary school or had completed Year 12. There was a weighted total of 1,612 records in this subset.
31 The second cohort includes Tasmanian government school students who were enrolled in Year 10 in 2008, a weighted total of 4,850. This analysis compared those who had completed Year 12 prior to Census (2,429) with those who left school without completing Year 12 (2,065). Those who were still attending secondary school (356) were excluded from the comparison.
Destinations and outcomes of Tasmanian Year 12 graduates
32 The Destinations and outcomes of Tasmanian Year 12 graduates article uses all school enrolments for students with a Year 12 Tasmanian government school enrolment record in the years from 2006 to 2010, and whose Census record indicated that they had completed Year 12. Only those who were aged 19 years or less when they completed Year 12 were included.
The weighted number of persons for each of these cohorts is in the following table.
WEIGHTED TOTAL NUMBER OF STUDENTS BY YEAR (a)
|
| 2006 | 2007 | 2008 | 2009 | 2010 |
|
|
| Population | 2,389 | 2,494 | 2,567 | 2,423 | 2,594 |
|
(a) For Destinations and outcome of Tasmanian Year 12 graduates article only.
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