Table 2.

Observed DED features and expected random DED features at the 33-ms time delay

Feature (sigma)	Observed	erf (x/2)	PI 1 − erf (x/2)	erf (x/2)N	PM 1 − erf (x/2)N	Expected random features in the DED map N × (1 − erf(x/2))
1	>8,000	0.68	0.31	0.0	1.0	216238
2	>8,000	0.95	0.05	0.0	1.0	31,007
3	3,167	0.997	0.002	0.0	1.0	1,839
4	1,018	1.0	0.0	0.0	1.0	43
5	264	1.0	0.0	0.67	0.33	0.4
6	44	1.0	0.0	1.0	0.0	0.0

Random features were estimated as a function of a multiple (x) of sigma (sigma level) in the unit cell of the SaBphP2 difference map calculated on an 88 × 88 × 88 grid (N = 681,472). The number of observed peaks was determined by the ccp4 program peakmax as a function of the DED sigma value. PM is the probability of observing at least one random feature equal to or more than a given sigma level in the entire map, as opposed to the probability PI of observing this random feature in an individual voxel. Note that we write (1 − erf) rather than using the equivalent erfc, where erf is the error function.