# Question

In a 1903 paper, 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 length of shell. She found the mean shell length of 461 randomly selected specimens of N. trivittata to be 11.9 mm. [SOURCE: "Quantitative Study of the Effect of Environment Upon the Forms of Nassa obsoleta and Nassa trivittata from Cold Spring Harbor, Long Island," Biometrika, Vol. 2, pp. 24-43]
a. Assuming that σ = 2.5 mm, obtain a 90% confidence interval for the mean length, μ, of all N. trivittata.