CIE A Level Maths: Probability & Statistics 2复习笔记2.3.2 E(X) & Var(X) (Continuous)
E(X) & Var(X) (Continuous)
What are E(X) and Var(X)?
- E(X)is the expected value, or mean, of a random variable X
- E(X) is the same as the population mean so can also be denoted by µ
- Var (X) is the variance of the continuous random variable X
- Standard deviation is the square root of the variance
How do I find the mean and variance of a continuous random variable?
How do I calculate E(g(X))?
Worked Example
Exam Tip
- A sketch of the graph of y = f(x) can highlight any symmetrical properties which can help reduce the work involved in finding the mean and variance
- Take care with awkward values and negatives – use the memory features on your calculator and avoid rounding until your final answer (if rounding at all!)
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