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An ecologist randomly samples 11 plants of a specific species and measures their heights. He finds that this sample has a mean of 18 cm and a standard deviation of 1 cm. If we assume that the height measurements are normally distributed, find a 90% confidence interval for the mean height of all plants of this species. Give the lower limit and upper limit of the 90% confidence interval. Carry your intermediate computations to at least three decimal places. Round your answers to one decimal place. (If necessary, consult a list of formulas.) Lower limit: X Upper limit