To transform a non-standard normal random variable into a standard normal random variable, you subtract the mean and divide by the variance.

(b) To transform a non-standard normal random variable into a standard normal random variable, you subtract the mean and divide by the variance. (c) The variance of the difference of two random variables is less than the sum of the variances if the covariance between the two random variables is negative. (d) When the covariates are independent of the treatment and the potential outcomes, the selection on (b) To transform a non-standard normal random variable into a standard normal random variable, you subtract the mean and divide by the variance. (c) The variance of the difference of two random variables is less than the sum of the variances if the covariance between the two random variables is negative. (d) When the covariates are independent of the treatment and the potential outcomes, the selection on