If a and b are two constants, then Var(a+bX) is________?

When data are collected in a statistical study for only a portion or subset of all elements of interest we are using?

The probability of even/odd numbers when a fair die is rolled is________?

For a certain distribution if ∑(x−2)=18,∑(x−24)=0,∑(x−28)=−24) then arithmetic mean is________?

Let Z1,Z2,....Zn be independent and identically distributedrandom variable, satisfying E[ι Zt ι]<∞. Let N be an integer valued random variable whose value n depends only on the values of the first n Z¡'s. Suppose E(N)< ∞, then E(Z1,Z2,....Zn)=E(N)E(Z) is called?

A chance variation in an observational process is________?