A Repeated-Measures Study Comparing Two Treatments with a Sample of N

A repeated-measures study comparing two treatments with a sample of n = 4 participants produces a mean of M = 18 with SS = 24 for the scores in the first treatment,a mean of M = 14 with SS = 18 for the scores in the second treatment,and a mean of M_D = 4 with SS = 12 for the difference scores.What is the estimated standard error for the sample mean difference?

A) 4
B) 3
C) 2
D) 1