Engineering Rock Mechanics

Questions and answers: anisotropy and inhomogeneity 1 6 1

The understanding of the correct use of the statistical terms 'resolu-

tion', 'accuracy', 'bias' and 'precision' is helpful for this procedure. We

give examples of their correct use here.

Resolution the number of digits used to specify a value, e.g. the value

of n can be given as 3,3.1,3.14,3.141, etc.

Accuracy the ability to obtain the correct answer on the average,

regardless of the spread of results.

Bias the difference between the sample mean and the true popu-

lation mean.

Precision the spread of results, regardless of whether they are accurate

or not.

The questions in this chapter have been included to emphasize the

anisotropy and inhomogeneity problem and to indicate procedures for

characterizing these features of the rock mass. We emphasize that the

DIANE nature of the rock should not be ignored by simply hoping that

a CHILE model is adequate.

10.2 Questions and answers: anisotropy and

inhomogeneity

410.1 On the rock mass photograph below, identify example fea-
tures that indicate that the rock mass is more DIANE than CHILE.