III. b. Field Calculator Option
             Estimated time:
             3 minutes
Calculating the 8 hour average ozone level in the new field just created. The Field Calculator allows you to calculate values within a data layer, possibly combining data from other layers or from multiple areas within the same layer.
In this exercise, you will:
  • Use the Field Calculator Option


                                                   Start VideoDemo

Text Version:

    1. In the Attribute Table Right Click in the EightHrAvg title -> Field Calculator -> Yes

    2. In the text box set the Field equal to ([HR8] + [HR9] + [HR10] + [HR11]+[HR12]+[HR13]+[HR14]+ [HR15])/8 -> Ok -> Close

    3. Note: The new Field will be on the far right of the attribute table, the values at the top of the table will be 0, this is because those are the border values for the ozone layer which have all been set to 0, scroll down a little bit to see if any values were calculated (if you used the above equation your first value after the zeros in the EightHrAvg column should be 70.881).Close the attribute table.

    4. Go back into the Layer properties for Ozone and set the value to the eight hour average (EightHrAvg), look for those points that have a value greater than 75, this represents ozone concentrations greater than 75 PPB, which is in violation of the 8 hour ozone exposure limit set by the EPA, how many ozone squares are out of compliance, can any visual relationships be drawn between the census tracts and the regions where ozone is out of compliance?

      Does it look like your chosen group live in better or worse areas?

      Look at the single hour you have been assigned, does it look like the group has an inordinate amount of exposure?

      Hey have you saved recently?!