Report card scoring
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Report Card Scoring. Several options under consideration for scoring and aggregating data. Why turn data into indices?. Integrate multiple measures into thematic scores Evaluate overall trends and compare locations Simplify communication with decision makers and the public. Four Main Steps.

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Report Card Scoring

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Report card scoring

Report Card Scoring

Several options under consideration for scoring and aggregating data


Why turn data into indices

Why turn data into indices?

  • Integrate multiple measures into thematic scores

  • Evaluate overall trends and compare locations

  • Simplify communication with decision makers and the public


Four main steps

Four Main Steps

  • Select and group indicators

  • Transform measured data into unit-less scores

  • Aggregate scores from multiple indicators into a summary index

  • Define breakpoints to bin index scores into descriptors of condition (grades or colors)


Central coast region preliminary indices

Central Coast RegionPreliminary Indices

  • Human Health WQ Index

  • Aquatic Life WQ Index

  • Toxicity Index

  • Bioassessment Index

  • Biostimulatory Risk Index

  • Habitat Index

  • Riparian Index


Indicators within indices

Indicators within Indices

Example from the Central Coast Region

1. Human Health Water Quality Index

Fecal Coliform

E. coli

Pathogens

Nitrate

Toxic chemicals


Indicators within indices1

Indicators within Indices

Example from the Central Coast Region

2. Aquatic Life Water Quality Index

Ammonia

Nitrate

Ortho-phosphate

DO departure

Toxic chemicals

Turbidity

Total dissolve solids

Total susp. sediment

pH departure


Scoring approach 1

Scoring Approach 1

Scoring into categories using multiple thresholds

If the mean > 20 then the color = Dark Red

If the mean > 10 and the mean <= 20 then the color = Red

If the mean > 5 and the mean <= 10 then the color = Orange

If the mean <= 5 then the color = Yellow

If the mean <= 1 and the max < 5 then the color = Green

If the mean <= 0.3 and the max < 1 then the color = Blue

This is the approach used on the CCAMP website


Scoring approach 2

Scoring Approach 2

Quotient Method

Divide measurement by a standard

Pro:+ scientific consensus behind standards

+ capture magnitude of excursion

Con:- no fixed upper end to scale

- appropriate standards must be available


Scoring approach 3

Scoring Approach 3

Magnitude and Exceedance Quotient (MEQ)

Combines two terms that express number of threshold exceedances and magnitude of exceendance.

Derived from Canadian Ministry of Governments method


Canadian ccme wq index

Canadian CCME WQ Index

Factor 1: Scope

Factor 2: Frequency

Factor 3: Amplitude


Canadian ccme wq index cont

Canadian CCME WQ Index, cont.

CCME WQ Index

Quadratic mean (or root mean square) gives greater weight to larger values, thus emphasizing excursions.


Canadian ccme wq index cont1

Canadian CCME WQ Index, cont.

Pro:+ widely excepted (esp. for drinking water)

+ considers scope, frequency, amplitude

Con:- resolution to detect differences among sites or times depends heavily on standards selected

- Not as useful for characterizing “healthy” because it only looks at failed tests

- Scope is susceptible to site variability in number of analytes tested (best for very consistent study design)


Meq modifications to ccme

MEQ: modifications to CCME

We are scoring all tests, not just failed tests. This provides a “good” end to the scoring tool

We eliminated the scope term (how many analytes fail) because we have inconsistent data availability across sites.

We do the calculations at the level of the analyte so that each analyte can also be scored


Calculating meq

Calculating MEQ

Calculate rate of exceedance (frequency) for each individual analyte (from CCME)

Factor 1: Frequency

F1

F1


Calculating meq cont

Calculating MEQ, cont.

Calculate magnitude (amplitude) for each individual analyte (from CCME)

Calculate unitless sample magnitudes:

Magnitude = concentration/threshold

Calculate normalized sum of magnitudes

NSM = Σ magnitudes / sample count

Scale from 0 – 100

= NSM / (0.01*magnitude average+0.01) 


Calculating meq cont1

Calculating MEQ, cont.

Combine exceedanceand magnitude factors and scale to 100 (modified from CCME)

MEQ = 100 – √exceedance2 + magnitude2

1.414


Aggregate scores into an index

Aggregate scores into an index

  • Number of standard excursions per site

  • Means: arithmetic, geometric, harmonic, quadratic

  • Worst case

  • Weights and penalty factors

  • Regression of simple to comprehensive indices

  • Empirical formulae


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