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Null hypothesis value


Computational notes

This procedure calculates the difference of an observed mean with a hypothesized value. A significance value (P-value) and 95% Confidence Interval (CI) of the observed mean is reported. The P-value is the probability of obtaining the observed mean in the sample if the null hypothesis value were the true value.

The P-value is calculated using the one sample t-test, with the value t calculated as:


or when the hypothesized mean is k and the standard deviation is s:


The P-value is the area of the t distribution with n−1 degrees of freedom, that falls outside ± t (see Values of the t distribution table).


  • Altman DG (1991) Practical statistics for medical research. London: Chapman and Hall.