E(X) of a random variable X, the theoretical mean of X. It is not based on the sample data but on the distribution of it. So, mean expectation value is a:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Parameter
$E(X)\; \text{is based on the probability distribution, not on sample data}$
$\text{Hence it describes a characteristic of the population}$
$\Rightarrow \text{Parameter}$
The mean expectation value is a parameter.