law of total variance


### **variance decomposition formula, conditional variance formulas** or **law of iterated variances** also known as **Eve's law**
decomposes the variance of two random variables on the same probability space into "explained" and "unexplained" components
$$Var(Y) = E[Var(Y|X)] + Var(E[Y|X])$$
EVPV(expected value of the process variance) + VHM (variance of the hypothetical means)
**Eve's law**, from the initials EV VE for "expectation of variance" and "variance of expectation".








