Solution :
Let
[tex]$k_1$[/tex] = number of levels for the factors 'flavors' = 4
(4 levels vanilla, chocolate, red velvet and marbled)
The degree of freedom for the factor 'flavors' = [tex]$k_1$[/tex] - 1
= 4 - 1
= 3
Now defining the F test statistics for testing the significance of the factors, 'flavors' :
F test statics = [tex]$=\frac{Ms\text{ (factor falvor)}}{Ms \text{ (errors)}}$[/tex] , Ms = mean square
where F = [tex]$F_{k_1-1}$[/tex], error df.
Thus the numerator degrees of the freedom for the F test statistics to determine if the factor flavor was significant is = [tex]$k_1$[/tex] - 1
= 4 - 1
= 3