I need to find the greatest and the least member of the set, and then subtract the least from the greatest. To compare fractions, I can either convert them to a common denominator, or compare their decimal equivalents. $\frac{3}{7}\approx 0.429$, $\frac{4}{3}\approx 1.333$, $\frac{11}{8}\approx 1.375$, and $\frac{6}{16}\approx 0.375$. I can see that $\frac{11}{8}$ is the greatest and $\frac{6}{16}$ is the least member of the set. To find their positive difference, I need to subtract $\frac{6}{16}$ from $\frac{11}{8}$. I can do this by converting them to a common denominator of 16. $\frac{11}{8}=\frac{22}{16}$, so $\frac{11}{8}-\frac{6}{16}=\frac{22}{16}-\frac{6}{16}=\frac{16}{16}$. This simplifies to 1. So the positive difference between the greatest and the least member of the set is 1. 
What is the positive difference between the greatest and the least member of the set $\left\{\frac{3}{7},\frac{4}{3},\frac{11}{8},\frac{6}{16}\right\}$? Express your answer in simplest form.