👉 Cooper's theorem, also known as the Coefficients of Variation Theorem, is a fundamental result in statistics and econometrics that relates the variance of two random variables with their means. It states that if X1, ..., Xn are independent and identically distributed (i.i.d.) random variables with mean μ and variance σ2, then: σ² = Σ(X_i - μ)² / n This theorem is significant because it allows us to calculate the standard deviation of