A collection of videos, activities and worksheets that are suitable for A Level Maths.

**What is the meaning of Var(X) and how to calculate it for a discrete random variable?**

**The Expected Mean E(X)**

The meaning of this function, Expected Mean E(X), and how to use it to calculate the expected mean for a discrete random variable.

**Extending E(X) to E(X ± a) and E(aX)**

What these functions mean, and how to use them.

**Variance : Var(X)**

The meaning of Var(X) and how to calculate it for a discrete random variable.

**Extending Var(X) to Var(X ± a) and Var(aX)**

I show you what these functions mean, and how to use them.

**Why does Var(a)=0, Var(X ± a) = Var(X) and Var(aX) = a ^{2}Var(X)?**

Non formal proof of these results.

**The meaning and calculation of E(X ^{2})**

In this tutorial I show you the meaning of this function and how to calculate it for a discrete random variable.

Try the free Mathway calculator and
problem solver below to practice various math topics. Try the given examples, or type in your own
problem and check your answer with the step-by-step explanations.

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