Per §10.4, the standard deviation σ in concrete cube testing uses (n -…

Question

Per §10.4, the standard deviation σ in concrete cube testing uses (n - 1) in the denominator under what name?

Accepted Answer

A. {'text': "Bessel's correction for the sample mean", 'label': 'A'}

1. §10.4 reads: 'The reason for using (n − 1) instead of n in denominator which is known as Bessel's correction is that the sum of the squares of deviations has minimum value when taken about the sample mean and is therefore smaller than it would be if taken about the population mean.'
2. IS 456-78 fixes the minimum sample for determining σ at 30 cubes.
_Source: IGNOU ET-522 Block-3 Unit-10 Concrete Mix Design, §10.4, p. 8_

Answer

{'text': 'Himsworth correction for risk factor', 'label': 'B'}

Answer

{'text': 'Gauss correction for histogram width', 'label': 'C'}

Answer

{'text': 'Abrams correction for w/c influence', 'label': 'D'}