BME 3721 Fall 2016 HW#3 Due 9/28/2016 Software can be used to calculate the answers, but show all equations used on all problems. 1. A researcher wishes to know if the amount of co-contraction between the ankle flexors and extensors as measured by Co-contraction index (CCI) predicts fall risk as measured by Four-square-step-test (FSST). CCI FSST 3.0 4.5 4.9 5.7 11.0 12.7 15.0 17.4 20.8 23.7 23.9 25.2 29.9 31.4 36.1 7 10 6 9 7 11 7 10 13 16 13 9 12 16 12 a) Calculate the linear regression: Y=a+bx b) Calculate the correlation coefficient r. c) Is the \"b\" coefficient statistically significant? (use alpha = 0.05) d) Is \"r\" significant? (use alpha = 0.05) e) What can the researcher conclude about the relationship between CCI and FSST? f) If we were to assume that the \"r\" value is significant, what proportion of variance in FSST scores is accounted for by the CCI score? 2. Short answer a.) What two things can you determine about a relationship using the r value? Y (Nervousness) 8 6 4 2 Y' = 0.9004X + 0.3053 0 0 2 4 6 8 X (Number of cups of coffee) 10 b. Using the data above, what is the expected nervousness score for someone who drank 5 cups of coffee? c. What is the critical r value for a two- tailed test when df = 18 and alpha = 0.01