Transportation Statistics and Microsimulation

262    ◾    Transportation Statistics and Microsimulation

standard error is .0316 mph. When we use the propagation of error formula we

have

S

X

X

2

2

0315/..=

As discussed in the literature, the jackknife formula is more accurate than

the propagation of error formula (see Efron and Tibshirani, 1993). In the authors’

experience, the jackknife standard error is also considerably easier to use than

deriving the propagation of error formula. The jackknife standard error has

degrees of freedom approximately equal to the number of unique pseudoval-

ues minus 1. This number is typically n – 1 except when calculating population

percentiles. When c