| Uncertainty information on the emission factors, activity
data and other parameters used for the analysis must be collected to create
probability density functions (for the Monte Carlo method) or mean and standard
deviation of the data (for the error propagation method). A probability density function describes the range and relative likelihood of possible values. Confidence limits give the range within which the underlying value of an uncertain quantity is thought to lie for a specified probability. This range is called the confidence interval. Click here to see probability density function graph. The Revised 1996 IPCC Guidelines suggest the use of a 95% confidence interval, which is the interval that has a 95% probability of containing the unknown true value. Actual statistical data should be used, where available, to empirically define the shape of the probability density functions. Where such empirical data are not available, expert judgment will be necessary. As this uncertainty data are collected, the correlations between parameters
(across source categories and across time) should also be considered. |
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