Mental Health A study was performed looking at the effect of physical activity on cognitive function among adults at high risk for Alzheimer's disease. There were 170 eligible subjects randomly assigned to either an exercise intervention (exercise group) or a control intervention (control group). The subjects were followed at 6-month intervals up to 18 months of follow-up. The primary assessment scale was the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog). The results at 18 months of follow-up among participants with mild cognitive impairment are given in the table below. (Let population 1 be the exercise group and population 2 be the control group. Use exercise group - control group.) Mean difference from baseline (18-month score minus baseline score) among participants with mild cognitive impairment in the ADAS-Cog score* Exercise group Control group Mean change -0.36 -0.46 95% CI (-1.35, 0.63) (-1.38, 0.46) 48 52 USE SALT (a) What is the standard deviation of change in the exercise group? (Round your answer to three decimal places.) (b) What is the standard deviation of change in the control group? (Round your answer to three decimal places.) (c) What test can be performed to compare the mean change in the two groups at 18 months? (You can use the Distribution Calculators page in SALT to check conditions.) O We should use a paired t test. O We should use a two sample t test for independent samples with unequal variances. O We should use a one sample z test. O We should use a two sample t test for independent samples with equal variances. O We should use a one sample t test