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PA Data Questions

What is P&A data?

Individual observations of Precision and Accuracy values are stored in separate tables of the AQS database to indicate the observed and expected precision and accuracy measurement responses for the various methods used to report sample data.  These observations of measurement values are collectively called "raw P&A data" because they are the actual, unprocessed values reported as opposed to the raw data sample values and summaries of those observations derived by AQS software.

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How do I get Precision and/or Accuracy data into AQS?

Users of AQS are able to upload precision and accuracy (P & A) data into the system by one of several ways:

  1. Online Correct: An AQS user can access the AQS application and select the heading entitled “Correct” on the “Main Menu”.    When the drop down menu appears on the screen, the user should select either Accuracy or Precision.  Upon selection of the data type that is to be entered, a template will appear on the screen.  The user can now populate the template with precision or accuracy data and click the “Save” button that is under the heading entitled “Action”.  The user should now go back to the “Main Menu” and select the heading entitled “Batch”.  At this time, the user should click on “Submit corrected data” to actually put data in AQS.
  2. Online Maintenance: An AQS user can access the system and select the heading entitled “Maintenance” on the “Main” Menu”.  When the drop down menu appears on the screen, the user should select either Accuracy or Precision.  Upon selection of the data type that is to be entered, a template will appear on the screen.  The user can now populate the template with precision or accuracy data and click the “Save” button that is under the heading entitled “Action”.  This will save data in AQS.  In the event the user has several records for input, each record must be entered individually and saved.
  3. Other Methods: Users of AQS have developed both spreadsheets and databases that will create a format acceptable for precision and accuracy transactions being loaded into AQS.  When an acceptable format is achieved, the user can run the batch load process in order to put data into AQS.
  4. The AQSP&A generator is one example of a stand-alone Excel workbook created by EPA staff to provide a simple way to create the 2 AQS data input transactions used for uploading accuracy data (transaction type RA) and precision data (transaction type RP). The transactions are created in the new AQS format with vertical bar delimiters.  A User Guide (pdf) for this approach is available from the "Manual and Guides" page.  Separate files for use in each EPA region are available from the P&A Data page.

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Why does the Accuracy Report (AMP247) show different percent differences for the same values?

The accuracy report rounds the actual and indicated values to one decimal place, when they are actually 2 decimal places in the database.  So if you calculate the percent differences using the rounded numbers, you will get numbers somewhat different from the values in the relative % difference column on the report, because the report is using the "un-rounded" values in the database.  A fix to show the 2 decimal places will be in a future version of the software - probably v2.8.

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Accuracy has "actual" vs. "indicated", but Precision uses the term "indicated" and "test". The "test" wording is confusing.

This occurs on the AQS Maintain forms for accuracy and precision data. The wording on the precision form uses the term "Test Concentration" to mean Actual Value for gaseous pollutants, and the term "Test Flow Rate" to mean Actual Value for precision flow checks.

(Added 5/31/05)

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AQS Frequent Questions | Technology Transfer Network | Air & Radiation


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