Workshop on Air Quality Data Analysis and Interpretation

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Workshop on Air Quality Data Analysis and
Interpretation

• Trend Determination by Linear Regression

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Frequency Distribution of Raw CO Data
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Linear Trend in Raw Hourly CO Data
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Frequency Distribution of Residuals
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Frequency Distribution of ln Transformed CO Data
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Frequency Distribution of Residuals for Fit of ln
Transformed Data
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Comparison of Trend Results Raw (Green) and ln
Transformed (Red) Data
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Interpretation of Trend Results

• Raw Data
• CO At B
• B value of CO from fit at t0
• ln Transformed Data
• ln CO at ß
• Transform back to normal CO vs. t
• CO eß eat
• Let b eß
• CO b eat

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Interpretation of Trend Results (continued)

• b value of CO from fit at t0
• The exponential term describes the exponential
  growth or decay of CO with time.
• From the fit ß -0.4219 or
• b 0.66 ppm
• and
• a -3.34 x 10-7 hr-1 -2.9 x 10-3 yr-1
• Decreasing at about 0.3/yr.