A certain psychological test measures empathy and emotional intelligence. The score, S, of a randomly selected senior student at a large university has a mean of 123 and a standard deviation of 29. The score, F, of a randomly selected first-year student at a large university has a mean of 104 and a standard deviation of 34. Suppose we randomly select one senior student and one first-year student. We can consider S and F to be independent random variables.

Calculate the standard deviation of the difference D = S – F.

σD = 17.7482
σD = 19
σD = 44.6878
σD = 227