In: Math
(a)
In case Happiness is categorized into: Extremely happy, Happy, Not happy, Very much unhappy :
Happiness is measured at Ordinal level because some kind of ranking is seen in the values.
(b)
In case Happiness is quantified in numerical values from 0 to 10: where Happiness is quantified in order of increase with 0 indicating total absence of Happiness and 10 indicating Complete Happiness.
Happiness is measured at Ratio level because value of 0 stands for absence of Happiness.
(c)
In case Happiness is quantified in numerical values from - 5 to +
5: where - 5 stands for Very much unhappy, - 1 stands for Not
happy, +1 stands for Happy and + 5 stands for Extremely happy:
Happiness is measured at Interval level because in such a quantification, value of 0 does not mean absence of Happiness and thus, 0 value is not defined and hence it is Interval level.
In the above explanation of (a), (b) and (c), we can replace Happiness by Depression and Anxiety.