Answer: c) 81
Step-by-step explanation:
The formula to calculate the degrees of freedom error for a one-way within-subjects ANOVA is given by :-
[tex]\text{df}=(n-1)\times(k-1)[/tex]
Given : A researcher recorded the shooting percentage of 28 professional basketball players in each of four quarters in a game.
Here , n= 28 and k= 4
Then, the degrees of freedom error for a one-way within-subjects ANOVA will be :-
[tex]\text{df}=(28-1)\times(4-1)=27\times3=81[/tex]
Hence, the degrees of freedom error for a one-way within-subjects ANOVA are 81.