8. The mean systolic blood pressure (SBP) at the end of the intervention for the 147 patients in the Individualized treatment cohort is 120 mmHg. The estimated sample standard deviation for these 147 SBP measurements is 19 mmHg. What does this standard deviation estimate quantify? a. The difference between the 75th and 25th percentiles of the SBP distribution for the 147 patients in the sample. b. The variability of the 147 individual SBP values in this sample (as an estimate of the variability of individual SBP values in the population represented by this sample) c. The variability in sample mean SBP across multiple random samples of 147 patients from the same patient population, who receive Individualized treatment. d. This is a trick question, as the sample standard deviation of these 147 sample SBP values cannot be computed from a single sample of 147 SBP values