A study of the relationship between age and various visual functions (such as acuity and depth perception) reported the following observations on the area of scleral lamina (mm2) from human optic nerve heads: 2.80 2.52 2.76 3.83 2.41 2.78 3.87 4.12 3.95 4.43 3.51 4.42 2.50 3.75 2.83 3.51 2.92 (a) Calculate xi and xi2. xi = 56.91 Correct: Your answer is correct. mm2 xi2 = 197.91 Incorrect: Your answer is incorrect. mm4 (b) Use the values calculated in part (a) to compute the sample variance s2 and then the sample standard deviation s. (Round your answers to four decimal places.) s2 = 0.4655 Incorrect: Your answer is incorrect. mm4 s = 0.6823 Incorrect: Your answer is incorrect. mm2