how to calculate variance for two periods how to measure variance of a random variable how to calculate variance in the future if a parameter is autocorrelational, what is the posterior value? what's the posterior of $y$ in a random variable how to determine the variance of an autocorrelated random variable how can i determine variance of a random variable how to determine the variance of a random variable what is the posterior of $a$? what is the probability of the posterior of $a$ how to calculate probability variance of an autocorrelation random variable what is the normal posterior of $a what is the variance of a random variable over time what is the parameter for y t? what is the parameter for probability in Bayesian estimation when will a normal value of the random variable be determined by the posterior? what does the posterior mean of $a$ when does the posterior of the variable $a$ update why is $y_t how to evaluate the variance of a random variable