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

C H A P T E R 9 P E R F O R M I N G A N A L Y S E S
9.3 Computing JRR Replicate Weights and Sampling Variance Using
SPSS and SAS
In this section example SAS and SPSS code that may be used to compute the JRR standard
errors for means and percentages is described. This code is provided in the form of SAS and
SPSS macros. These macros compute the percentage of students within a subgroup defined
by a set of classification variables, the JRR standard error of this percentage, the mean for the
group on a variable of choice, and the JRR standard error of that mean.
Each of these macros operate as follows:
1. Computes a set of 75 replicate weights for the record using the procedure described in the
previous chapter.
2. Aggregates or summarizes the file computing the sum of the weights for each category,
the sum of the weights overall, and the sum of a weighted analysis variable.
3. Computes the percent of people within each group, their mean on the analysis variable,
and their corresponding standard errors. In SPSS the resulting working file contains the
corresponding statistics. In SAS the file FINAL contains the corresponding statistics.
When using each of these macros, the user needs to specify a set of classification variables,
one analysis variable, the number of replicate weights to be generated, the variable that
contains the sampling information such as JKZONE and JKINDIC, and the sampling weight
that is to be used for the analysis. When using the SAS macro the user will also need to
specify the data file that contains the data that is to be processed. In SPSS the macro uses the
current working file, which is the file that was last read.
9.3.1 SAS Macro for Computing Mean and Percents with
Corresponding Standard Errors (JACK.SAS)
The CD containing the TIMSS International Database contains a SAS macro program called
JACK.SAS. This macro can be used to compute weighted percents and means within
categories defined by variables specified by the user, and the JRR standard error estimate for
these statistics. The control code for the macro JACK.SAS is presented in Figure 9.5.
9 - 8 T I M S S D A T A B A S E U S E R G U I D E