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: 2.72 2.71 2.64 3.94 2.31 2.64 3.86 4.29 3.85 4.29 3.44 4.62 2.34 3.66 2.79 3.57 2.92 IЛ USE SALT (a) Calculate Ex, and Σx². Σχο Σχι 2 = = mm² 4 mm (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.) $2 S = mm4 mm²

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: 2.69 2.61 2.70 3.77 2.29 2.76 3.99 4.22 3.96 4.42 3.48 4.57 2.53 3.61 2.73 3.55 2.93 Ex, = Ex² = USE SALT (a) Calculate Ex, and Ex, 2. mm2 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 = mm S= mm²

Q12

15. Does learning a second language change brain structure? Mechelli et al. (2004) tested 22 native Italian speakers who had learned English as a second language. Proficiencies in reading, writ- ing, and speech were assessed using a number of tests whose results were summarized by a profi- ciency score. Gray-matter density was measured in the left inferior parietal region of the brain using a neuroimaging technique, as mm³ of gray matter per voxel. (A voxel is a picture element, or "pixel," in three dimensions.) The data are listed in the accompanying table. a. Display the association between the two variables in a scatter plot. b. Calculate the correlation between second language proficiency and gray-matter density. c. Test the null hypothesis of zero correlation. d. What are your assumptions in part (c)? e. Does the scatter plot support these assump- tions? Explain. Proficiency score for Gray-matter second density language (mm³/voxel) 0.26 0.44 0.89 1.26 1.69 1.97 1.98 2.24 2.24 2.58…