A biologist wants to estimate the difference between the mean body lengths of green and brown stinkbugs. a random sample of 20 green stinkbugs has a mean body length of 16. 22 millimeters (mm) and a standard deviation of 1. 34 mm. a random sample of 20 brown stinkbugs has a mean body length of 13. 41 mm and a standard deviation of 0. 73 mm. what is the standard error of the difference (green - brown) between the sample means?