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Scenario Attribute Summary Options with Snapshots

The following describes report statistics and options for a scenario attribute summary assuming non-cumulative mode. Use it to analyze your report statistics.

• Final Value–The value of the attribute at the snapshot.

• Minimum–The minimum value over the snapshot interval.

• Maximum–The maximum value over the snapshot interval.

• Observations–The number of times the attribute was assigned a value over the snapshot interval.

• Total–The total value of the attribute, calculated by summing the value after each assignment over the snapshot interval. This is used to calculate the Average value of the attribute.
  
  Example: An attribute is assigned the value 2, then 3, and then 5. The total value is 2+3+5=10.

• Average–The average value of the scenario attribute over the snapshot time interval. This is calculated by summing the value (Total) of the attribute and dividing by the observations.
  
  Example: An attribute is assigned the value 2, then 3, and then 5. The average value of the attribute is (2+3+5) / 3 = 3.33. Another way to express this is Total / Observations.

• Total Time of Observations–The elapsed time of the snapshot interval.

• Time Weighted Average–The average value weighted by the length of time it held each value. Another way to express this is the “Time Weighted Total” / “Total Time of Observations”. The Time Weighted Total is the sum of the values times the length of time it held each value.
  
  Example: An attribute is assigned the value 2 for 10 seconds, then 3 for 10 seconds, and then 5 for 5 seconds.
  
  The Time Weighted Total is ((2*10)+(3*10)+(5*5)) = 75
  
  The “Time Weighted Average” is “Time Weighted Total” / “Total Time of Observations”= 75/25 = 3

• Standard Deviation–The root mean square (RMS)
  
  Example: An attribute is assigned the value 2, then 3, and then 5. The sample mean or average value of the attribute is (2+3+5) / 3 = 3.33.
  
  The deviation of each value from the sample mean is (2-3.33), (3-3.33), and (5-3.33). The total of the squared deviations is (-1.33)^2 + (0.33)^2 + (1.67)^2 = 4.667. The unbiased estimation of the variance is 4.667/(3-1) = 2.3335.
  
  The standard deviation is the square root of 2.3335 which is 1.5276.

• Time Weighted Average Standard Deviation–The root means square deviation of the values from the Time Weighted Average.
  
  Example: An attribute is assigned the value 2 for 10 seconds, then 3 for 10 seconds, and then 5 for 5 seconds. The time weighted average value of the attribute is ((2*10)+(3*10)+(5*5)) / (10+10+5) = 75/25 = 3
  
  The deviation of each value from the time weighted average is (2-3), (3-3), and (5-3). The unbiased estimation of the time weighted variance is
  
  (((-1)2 *10)+((0)2*10) +((2)2 * 5)) / 25 = 1.200
  
  The time weighted standard deviation is the square root of 1.2 which is 1.0954