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Appendix A<br />

GLOSSARY OF STATISTICAL AND GHG INVENTORY TERMS, cont<strong>in</strong>ued<br />

TERM STATISTICAL DEFINITION GHG INVENTORY APPLICATION<br />

LINEAR<br />

REGRESSION<br />

LOGNORMAL<br />

DISTRIBUTION<br />

MEAN<br />

MEASUREMENT<br />

MEDIAN<br />

MONTE CARLO<br />

METHOD<br />

NORMAL<br />

DISTRIBUTION<br />

OUTLIER<br />

POPULATION<br />

PRECISION<br />

L<strong>in</strong>ear regression provides a way of fitt<strong>in</strong>g a<br />

straight l<strong>in</strong>e to a set of observed data po<strong>in</strong>ts,<br />

tak<strong>in</strong>g <strong>in</strong>to account the effects of<br />

observational variability.<br />

This is an asymmetric distribution, which<br />

starts from zero, rises to a maximum <strong>and</strong><br />

then tails off more slowly to <strong>in</strong>f<strong>in</strong>ity.<br />

The average of two or more observed<br />

values.<br />

The sample mean, or arithmetic average, is<br />

an estimator for the mean.<br />

The median, or population median, is the<br />

50 th population percentile.<br />

For symmetric distributions it equals the<br />

mean.<br />

The pr<strong>in</strong>ciple of Monte Carlo analysis is to<br />

perform the <strong>in</strong>ventory calculation many<br />

times, where each time the uncerta<strong>in</strong><br />

emission factors or model parameters <strong>and</strong><br />

activity data are chosen r<strong>and</strong>omly (by the<br />

computer) from with<strong>in</strong> the distribution of<br />

uncerta<strong>in</strong>ties specified <strong>in</strong>itially by the user.<br />

The normal (or Gaussian) distribution has a<br />

probability density function that can be<br />

def<strong>in</strong>ed by two parameters (the mean <strong>and</strong><br />

the st<strong>and</strong>ard deviation).<br />

The population is the totality of items under<br />

consideration. In the case of a r<strong>and</strong>om<br />

variable, the probability distribution is<br />

considered to def<strong>in</strong>e the population of that<br />

variable.<br />

The degree to which data with<strong>in</strong> a set<br />

cluster together.<br />

For example, if emissions observations<br />

are plotted aga<strong>in</strong>st correspond<strong>in</strong>g<br />

activity levels, the slope of the l<strong>in</strong>e<br />

fitted by a l<strong>in</strong>ear regression provides an<br />

estimate of the appropriate emission<br />

factor.<br />

Procedure for determ<strong>in</strong><strong>in</strong>g a value for a<br />

physical variable.<br />

Uncerta<strong>in</strong>ties <strong>in</strong> emission factors <strong>and</strong>/or<br />

activity data are often large <strong>and</strong> may<br />

not have normal distributions. In this<br />

case the conventional statistical rules<br />

for comb<strong>in</strong><strong>in</strong>g uncerta<strong>in</strong>ties become<br />

very approximate.<br />

Monte Carlo analysis can deal with this<br />

situation by generat<strong>in</strong>g an <strong>uncerta<strong>in</strong>ty</strong><br />

distribution for the <strong>in</strong>ventory estimate.<br />

A result that differs considerably from<br />

the ma<strong>in</strong> body of results <strong>in</strong> a set.<br />

Precision is the <strong>in</strong>verse of <strong>uncerta<strong>in</strong>ty</strong><br />

<strong>in</strong> the sense that the more precise<br />

someth<strong>in</strong>g is, the less uncerta<strong>in</strong> it is.<br />

Pilot Version, September 2009 A-3

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