Per §10.4 and IS 456-78, the minimum sample size to determine the stan…

Question

Per §10.4 and IS 456-78, the minimum sample size to determine the standard deviation σ for concrete is:

Accepted Answer

B. {'text': 'At least 30 test results', 'label': 'B'}

1. §10.4: 'For determination of σ at least 30 samples are to be taken as per IS 456 - 78.'
2. The same section caps the coefficient of variation V = (σ/μ) × 100 at 15 percent for acceptable concrete production.
_Source: IGNOU ET-522 Block-3 Unit-10 Concrete Mix Design, §10.4, p. 8_

Answer

{'text': 'At least 10 test results', 'label': 'A'}

Answer

{'text': 'At least 20 test results', 'label': 'C'}

Answer

{'text': 'At least 100 test results', 'label': 'D'}