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

P E R F O R M I N G A N A L Y S E S C H A P T E R 9
specified continuous variable. These macros also generate replicate weights and compute
JRR sampling variance for the percent and mean estimates. Although, in general, the
continuous variable of choice will be one of the achievement scores in either mathematics
or science, this continuous variable can be any other continuous variable in the file. How
to use each of these macro programs is described later in this chapter.
EXAMPLE1.SAS, EXAMPLE2.SAS and EXAMPLE3.SAS
EXAMPLE1.SPS, EXAMPLE2.SPS and EXAMPLE3.SPS
These are the programs used in the examples presented later in this chapter. These
programs are included only in the CD for Population 2, although the same examples can
be easily adapted to perform the same analyses with the Population 1 data.
ASASCORE.SAS, BSASCORE.SAS, ASPSCORE.SAS, BSPSCORE.SAS
ASASCORE.SPS, BSASCORE.SPS, ASPSCORE.SPS, BSPSCORE.SPS
These files contain control code in SAS and SPSS that can be used to convert the
response codes to the cognitive items discussed in Chapter 7 to their corresponding
correctness score levels. The use of these programs is described later in this chapter.
The files beginning with the letters ASA and BSA can be used to recode the items from
the written assessment. Those beginning with the letter ASP and BSP can be used to
recode the items from the performance assessment.
9.2 Creating SAS Data Sets and SPSS System Files
The CD contains SAS and SPSS control code to read each one of the ASCII data files and
create a SAS data set or an SPSS system file. An extract of the main sections of the control
code for reading the Student Background data file using SAS is presented in Figure 9.3, and
for creating the file in SPSS in Figure 9.4. Each of these files contain information on the
location for each variable in the file, its format, a descriptive label for each variable and their
categories (in the case of categorical variables), and code for handling missing data. The
control and data files have been created to facilitate access of the data on a country by
country basis. The command lines in the control files should be edited to produce programs
that will create SAS or SPSS files for any specified country. While most of the program code
is functional, users will need to edit input and output file names. Performing analyses that
require the data from more than one country will necessitate merging the respective data files
into a larger one. Alternatively, the user can access the data and compute the necessary
statistics on a country by country basis by reading one file at a time, computing the necessary
statistics, and then moving on to the next country’s data. The method chosen by the user will
depend greatly on the storage and processing capacity of the computer system that is used.
For the examples that we present in this User Guide we have combined the data files of
individual countries into one larger data file that contains the data for all participating
countries.
T I M S S D A T A B A S E U S E R G U I D E 9 - 5