Degrees Of Freedom — Why it is n-1 ?

P.S. Contingency Table: In statistics, a contingency table (also known as a cross tabulation or cross-tab, Pivot table that we use in Excel) is a type of table in a matrix format that displays the (multivariate) frequency distribution of the variables.

Conclusion:

Degrees of freedom of a data set is n — k, whereas n — Size of data set & k — Number of constraints placed.

As the constraints increase, freedom is reduced.

If there is more than one variable are combined into a matrix, then the entire degrees of freedom is the product of degrees of freedom of each variable.