The mean of 8 observations is fixed at 15. The number of observations that are free to vary, that is, the number of degrees of freedom, is
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 7
Since the mean of the 8 observations is 15, their total is fixed:
\(8 \times 15 = 120\)
Any 7 of the observations can be chosen freely. The 8th must then be 120 minus the sum of the other 7, so it is not free.
So the degrees of freedom are 8 − 1 = 7.