Evaluation of Sampling

Experimental tests of sampling techniques are compared in Table 2 as an example. Binary mixtures of coarse and fine sand (60:40 ratio) were examined (Ref 2) using various laboratory sampling techniques. In every case, 16 samples were examined to give the standard deviations shown in column 2. It may be deduced that very little confidence can be placed in the first three techniques and that the rotary sample divider is so superior to all other methods that it should be used whenever possible.

Table 2 Reliability of selected sampling methods using a 60:40 sand mixture

Sampling technique

Standard deviation, %

Coning and quartering

6.81

Scoop sampling

5.14

Table sampling

2.09

Chute slitting

1.01

Rotary sample dividing

0.146

Random variation

0.075

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