In 1903, a paper published by abigail camp dimon, discussed the effect of environment on the shape and form of two sea snail species. nassa obsoleta and nassa trivittata. one of the variables that dimon considered was the length of the shell. she found that the mean shell lenth of 461 randomly selected specimens of n. trivittata to be 11.9 mm., with a standard deviation of 2.5 mm. (source: elementary statitics, weiss, 8th edition) if you were to construct a confidence interval for the average shell length for the n. trivittata species, what is the standard error used to calculate the margin of error? (do not round any values except your final answer. round your answer to the thousands place)