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TRI Statistics

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Easy to Use!

Statistical functions are easy to use. Just click on the box for the statistics you want to see. The database will automatically calculate the statistical value (sum, count, max, min, etc.) for the other columns (which taken together comprise a statistical group) that you have selected. This may be a difficult concept to understand but it is easily illustrated in the examples below.

Examples:

How do I sum releases by Zone Improvement Plan (ZIP) code?

  1. Select the Chemical Discharge to Water view.
  2. Select the ZIP code column, then select the SUM box from the "Group Functions for Release Estimate Amount". DO NOT SELECT THE RELEASE ESTIMATE COLUMN LOCATED DIRECTLY ABOVE THE STATISTICAL FUNCTION BOXES. Click on the Step 3: Enter Selection Criteria button at the bottom of the screen.
  3. Enter the ZIP code you would like to sum by in the Search Value column for ZIP code.
  4. After you enter your selection criteria, execute the search by clicking on the "Search Database" button.

How do I sum releases by chemical, media (AIR, WATER, LAND, etc.), and ZIP code?

  1. Select the Combined Releases view.
  2. Select the Chemical Name.
  3. Select Category (Media) of the Release.
  4. Select ZIP code.
  5. Select the SUM box from the "Group Functions for Release Estimate Amount".
  6. Enter any additional columns you want to sum by like city, state, county, or ZIP code. Don't enter columns like "TRI Facility ID" or "Document Control Number".
  7. Go to Step 3 and enter your selection criteria and then execute the search by clicking on the "Search Database" button.

Statistical Views

Although the statistical functions are powerful, it takes processing time for the database to calculate the requested statistics. To give better response times, we have precalculated some State and Facility level statistics. These statistical views are available through the EZ Search and Customized Search.

  • Facility Summary: Release estimate statistics, for both releases and transfers, categorized by facility, media, and reporting year.
  • State Chemical Summary: Release estimate statistics, for both releases and transfers, categorized by State, chemical, and reporting year.
  • State Summary: Release estimate statistics, for both releases and transfers, categorized by release or transfer type (Air stack, Air fugitive, water, land, etc) and reporting year.

Statistical Function Definitions

SUM
This function gives you the sum of the selected variable (usually release estimate) for each unique "group" value. If you selected city, state, and the "Sum Function for Release Estimate", then a "Release Estimate Sum" will be reported for each unique combination of city and state.

AVERAGE
This function gives you the arithmetic mean of the selected statistical variable for each unique "group" value. This is computed by taking sum of the group and dividing it by the number of individual rows in the group.

COUNT
This function gives you the total number of individual rows for each unique "group" value. Selecting this gives you a good indication of how many rows resulted from your selection criteria. If all the counts are 1, then you have selected variables that resulted in the group value and the single number value being the same, giving you a meaningless group value.

MAX
This function gives you the highest value in the group.

MIN
This function gives you the lowest value in the group. It ignores null values.

STANDARD DEVIATION
This function gives you the deviation from the average or the mean. This allows you to determine whether certain row values are out of proportion to the others, giving you an average that is much higher than the mean.

VARIANCE
This function gives you the variance of all values for a group of rows.