Reads in the unzipped files downloaded from the TIMSS international
database(s) using the IEA Study Data Repository.
Data files require the SPSS data file (.sav) format using the default
filenames.
A TIMSS edsurvey.data.frame includes three distinct data levels:
When the getData function is called using a TIMSS edsurvey.data.frame,
the requested data variables are inspected, and it handles any necessary data merges automatically.
The school data always will be returned merged to the student
data, even if only school variables are requested.
If teacher variables are requested by the getData call, it
will cause teacher data to be merged.
Many students can be linked to many teachers, which varies
widely between countries.
Please note that calling the dim function for a TIMSS
edsurvey.data.frame will result in the row count as if the
teacher dataset was merged.
This row count will be considered the full data N of the
edsurvey.data.frame, even if no teacher data were included in an analysis.
The column count returned by dim will be the count of unique column
variables across all three data levels.
Beginning with TIMSS 2015, a numeracy dataset was designed to assess
mathematics at the end of the primary school cycle
for countries where most children are still developing fundamental mathematics skills.
The numeracy dataset is handled automatically for the user and is
included within the fourth-grade dataset gradeLvl=4.
Most numeracy countries have a 4th grade dataset in addition
to their numeracy dataset, but some do not.
For countries that have both a numeracy and a 4th grade dataset,
the two datasets are combined into one edsurvey.data.frame for that country.
Data variables missing from either dataset are kept, with NA values
inserted for the dataset records where that variable did not exist.
Data variables common to both datasets are kept as a single data variable,
with records retaining their original values from the source dataset.
Consult the TIMSS User Guide for further information.