- In some browsers, parts of the CHAD Oracle-generated display may disappear after scrolling up and
down. If this happens, simply press your browser's Refresh or Reload button.
- To search for records from Washington, D.C., enter "DC", without the quotes, in the State field on the
Questionnaire Query page.
- The File Output Option on the Questionnaire Query page
must be exercised on a study-by-study basis or with an age range of no more than 6 years.
- A much more complete description of CHAD and how to use it is available on the
- CHAD and this web site have three levels of data: raw data, raw values, and combined values.
- Raw Data: These are the data files which most closely match those
generated during the original studies. In some cases these files
were not available and secondary or paper sources were used. These
are generally stored as ASCII data files and can be downloaded from
the Download page.
- Raw Values: These data have been integrated into CHAD Access. Every attempt has
been made to use the original coding and generally include all of the data pertinent to CHAD.
These data are only available in CHAD Access, not online in CHAD Oracle.
- Combined Values: The common parts of the studies are represented in the
consolidated CHAD database. In many cases some generalization was
required to combine the data in a usable format. Some of the specifics of the studies are lost in the combined data. The
combined data are available online through CHAD Oracle and in CHAD Access.
- Two versions of the CHAD Access application can be downloaded and run on a Windows PC. See the
Download page. These contain the full set of raw
values from each study and the combined CHAD database. This application also offers some additional
functionality. More information on these applications can be found on the
About CHAD for PC page.
- The raw data files from each study, typically in compressed ASCII format, are available on the
Download page. Since these were gathered from
many separate studies, the format and documentation is highly variable.
- The raw values from individual studies can provide a wealth of detailed information not available in the consolidated CHAD database.
However, it is more difficult to utilize this data. This data is only available in the CHAD Access (Windows) version. The User's
Manual has some examples.
- Many of the studies in CHAD did not attempt to draw a random sample of people. Therefore, a sample of people from the database
will not be representative of the whole US population or their activities under different conditions (e.g., warm vs. cool weather).
The most representative study in the database is NHAPS with over 9,000 diary days of information. However, even this data was not
truly randomly sampled. For instance weekend days were over sampled. The NHAPS study documentation describes methods to
account for some of these biases.
- Three new criteria for removing CHADIDs from the database were established - Age missing; Gender missing and Age
greater than 11; and Location missing for greater than 239 minutes regardless of whether activity information was available
or not. Applying these criteria resulted in the removal of 252 CHADIDs.