To use a paired t confidence interval to estimate the population mean difference in responses, or to perform a paired t test regarding hypotheses about the population mean difference, there are some assumptions (or conditions). Which of the following is a (are) required assumption(s)? Select all that apply.
i. The two sets of measurements that are used to form the pairs are independent random samples.
ii. The number of paired observations (or differences) is more than 30.
iii. The distribution of the population of all differences in responses is normal.
iv. The standard deviation for the population of all differences is known.