Industrial engineers who specialize in ergonomics are concerned with designing workspace and devices operated by workers so as to achieve high productivity and comfort. The article "Studies on Ergonomically Designed Alphanumeric Keyboards" (Hum. Factors, 1985: 175-187) reports on a study of preferred height for an experimental keyboard with large forearm-wrist support. A sample of n = 31 trained typists was selected, and the preferred keyboard height was determined for each typist. The resulting sample average preferred height was x = 80 cm. Assuming that the preferred height is normally distributed with = 2.0 cm (a value suggested by data in the article), obtain a CI for , the true average preferred height for the population of all experienced typists.