Suppose that all the values in a data set are converted to z-scores. which of the statements below is true? a: the mean of the z-scores will be zero, and the standard deviation of the z-scores will be the same as the standard deviation of the original data values. b: the mean and standard deviation of the z-scores will be the same as the mean and standard deviation of the original data values. c: the mean of the z-scores will be 0, and the standard deviation of the z-scores will be 1. d: the mean and the standard deviation of the z-scores will both be zero.