Asample of size 20 has been taken from a population. A 95% condence interval will be constructed using the Student's tdistribution tomgnlg critical value when O the underlying population is Normally distributed and the population standard deviation is unknown 0 the underlying population is not Normally distributed, the Central Limit Theorem does not hold and the population standard deviation is unknown 0 the underlying population is not Normally distributed but the Central Limit Theorem holds and the population standard deviation is known 0 the underlying population is Normally distributed and the population standard deviation is known Ordinal variables are .. . O Numerical and can be added or subtracted O Categorical and can be ordered O Numerical and can be multiplied or divided O Categorical without implying order