Test Coefficient of Variation

The Test Coefficient of Variation corresponding to a Test Range is obtained from the Standard Deviation of the Test Specimen Strengths. The Standard Deviation of the Test Specimen Strengths is computed according to ACI 214-77 (References 2) formula (3.4) as the Test Range divided by a factor d₂, which depends on the number of Test Specimen Strengths.

The factor d₂ equals:

1.128 for 2 strength values.

1.693 for 3 strength values.

A Test Coefficient of Variation is expressed as a percentage and is therefore calculated as:

100R_T/(d₂S_T)

Where:

R_T = the corresponding Test Range

S_T = the corresponding Test Strength