<p>just one more</p>
<p>Random variable X is normally distributed with mean 10 and standard deviation 3 and random variable y is normally distributed with mean 9 and standard deviation 4. if x and y are independent, which of the following describes the distribution of Y-X</p>
<p>B. Normal with mean -1 and standard deviation 1
C. normal with mean -1 and standard deviation 5</p>
<p>So if i put it into my calculator (X= L1 = 4,7,10,13,16; Y=L2 = 1,5,9,13,17) and subtract L2-L1 i get (-3,-2,-1,0,1), which has a sd of 1. However if i use the formula (root(3^2 +4^2)) i get sd as 5. Which ones the right answer?</p>