1. Do the formulae for the mean and variance of a linear function of a random variable have to be memorised?
The formulae are provided for many exams, but as with all formulae it is useful to know them. Check with your teachers or examination board.
2. Do I have to use the formulae to find the mean and variance of a linear function of a random variable?
Not necessarily. If the probability distribution table is given, the values of the variable can be placed into the function and then E(X) and VAR(X) worked out in the usual manner.
