The given data:
51, 37, 83, 44, 52, 19, 99, 7, 36.
It is given that, the formula to find the mean:
[tex]\bar{X}=\frac{1}{n}\sum ^n_{j\mathop=0}X_j[/tex]Here, n represents the number of observations.
Hence, the value of n is 9.
Therefore, the correct option is C.