## What is the formula for expected value?

The basic expected value formula is the probability of an event multiplied by the amount of times the event happens: (P(x) * n).

## How do you find the expected value of an expected value?

In statistics and probability analysis, the expected value is calculated by multiplying each of the possible outcomes by the likelihood each outcome will occur and then summing all of those values.

**What is the expected value of random variable?**

The expected value of a random variable is denoted by E[X]. The expected value can be thought of as the “average” value attained by the random variable; in fact, the expected value of a random variable is also called its mean, in which case we use the notation µX.

**How do you find the expected value example?**

Expected value is the probability multiplied by the value of each outcome. For example, a 50% chance of winning $100 is worth $50 to you (if you don’t mind the risk). We can use this framework to work out if you should play the lottery.

### How do you solve for the expected value of a random variable?

For a discrete random variable, the expected value, usually denoted as or , is calculated using: μ = E ( X ) = ∑ x i f ( x i )

### What is the expected value of a constant?

The expected value of a constant is just the constant, so for example E(1) = 1. Multiplying a random variable by a constant multiplies the expected value by that constant, so E[2X] = 2E[X].

**Is expected value of a random variable a constant?**

**How do you calculate the expectation of product of two random variables?**

Multiplying a random variable by any constant simply multiplies the expectation by the same constant, and adding a constant just shifts the expectation: E[kX+c] = k∙E[X]+c . For any event A, the conditional expectation of X given A is defined as E[X|A] = Σx x ∙ Pr(X=x | A) .

## How do you know whether a random variable is continuous?

A discrete random variable has a countable number of possible values. The probability of each value of a discrete random variable is between 0 and 1, and the sum of all the probabilities is equal to 1. A continuous random variable takes on all the values in some interval of numbers.

## How do you calculate expected frequency?

Expected Frequency = (Row Total * Column Total)/N. The top number in each cell of the table is the observed frequency and the bottom number is the expected frequency.

**How do you find the expected value of a discrete random variable?**

**How to calculate the expected value of a random variable?**

Note that the interpretation of each is the same as in the discrete setting, but we now have a different method of calculating them in the continuous setting. If X is a continuous random variable with pdf f(x), then the expected value (or mean) of X is given by μ = μX = E[X] = ∞ ∫ − ∞x ⋅ f(x)dx.

### How to calculate the variance of a continuous random variable?

For the variance of a continuous random variable, the definition is the same and we can still use the alternative formula given by Theorem 3.7.1, only we now integrate to calculate the value: Var (X) = E [ X 2] − μ 2 = (∫ − ∞ ∞ x 2 ⋅ f (x) d x) − μ 2 Example 4.2. 1

### What is the expected value of the PDF of X?

The pdf of X was given by E[X] = 1 ∫ 0x ⋅ xdx + 2 ∫ 1x ⋅ (2 − x)dx = 1 ∫ 0x2dx + 2 ∫ 1(2x − x2)dx = 1 3 + 2 3 = 1. Thus, we expect a person will wait 1 minute for the elevator on average.