User Guide for the TIMSS International Database.pdf - TIMSS and ...

C H A P T E R 7 D A T A B A S E F I L E S
Other Variables in the Reliability Files
In addition to the coding reliability variables, the reliability files also include identification
variables to aid in case identification. Some tracking variables are also included that were used in
conducting of the coding reliability study within each country, including the reliability booklet set
to which each student was assigned (ITBSET) and the identification of the first and second coders
(ITCODE, ITCODE2). 8
7.2.4 Student-Teacher Linkage Files
General Information
The Student-Teacher Linkage files for Population 1 and Population 2 contain information
required to link the student and teacher files and to compute appropriately weighted teacher-level
data using the student as the unit of analysis. Example analyses using these data files are
described in Chapter 9.
The Student-Teacher Linkage files contain one entry per student-teacher linkage combination in
the data. In many cases, students are linked to more than one mathematics and/or science teacher,
and in these cases there will be one record for each student-teacher link. This is particularly true
in Population 2, where the majority of students have separate teachers for science and
mathematics. In addition, in some countries many students may also have more than one teacher
for each of the two subject areas. For instance, if three teachers are linked to a student, there are
three entries in the file corresponding to that student.
Variables Required for Computing Teacher-Level Data
The following important variables required to compute appropriately weighted teacher-level data
are included in the linkage files.
NMTEACH Number of mathematics teachers for each student
NSTEACH Number of science teachers for each student
NTEACH Number of total teachers for each student (mathematics and science)
MATWGT Adjusted weight for mathematics teacher data
SCIWGT Adjusted weight for science teacher data
TCHWGT Adjusted weight for total teachers (mathematics and science)
The MATWGT, SCIWGT, and TCHWGT variables contain mathematics, science, and total
teacher weights adjusted for the total number of teachers of each type for each student. For
example, if a student has three mathematics teachers, the adjusted weight for each mathematics
teacher (MATWGT) will be equal to one-third so that each mathematics teacher contributes
equally to the teacher-based data for students.
8 See Mullis and Smith (1996) for more detailed information about the coding reliability procedures and results.
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