How do you find the expected value given the mean and standard deviation?

For each value x, multiply the square of its deviation by its probability. (Each deviation has the format x – μ). The mean, μ, of a discrete probability function is the expected value. The standard deviation, Σ, of the PDF is the square root of the variance.

How do you add two variances?

The Variance Sum Law- Independent Case Var(X ± Y) = Var(X) + Var(Y). This just states that the combined variance (or the differences) is the sum of the individual variances. So if the variance of set 1 was 2, and the variance of set 2 was 5.6, the variance of the united set would be 2 + 5.6 = 7.6.

How does mean and variance change when multiplying?

Adding a constant value, c, to a random variable does not change the variance, because the expectation (mean) increases by the same amount. Rule 3. Multiplying a random variable by a constant increases the variance by the square of the constant.

Is variance of sum sum of variances?

For independent random variables X and Y, the variance of their sum or difference is the sum of their variances: Variances are added for both the sum and difference of two independent random variables because the variation in each variable contributes to the variation in each case.

How do you change variance?

Variance

1. Work out the Mean (the simple average of the numbers)
2. Then for each number: subtract the Mean and square the result (the squared difference).
3. Then work out the average of those squared differences. (Why Square?)

How do you find the mean variance and standard deviation given N and P?

Binomial Distribution

1. The mean of the distribution (μx) is equal to n * P .
2. The variance (σ2x) is n * P * ( 1 – P ).
3. The standard deviation (σx) is sqrt[ n * P * ( 1 – P ) ].

What is the expectation formula?

The basic expected value formula is the probability of an event multiplied by the amount of times the event happens: (P(x) * n). The formula changes slightly according to what kinds of events are happening.