Study investigators collect standardized data on timed 24 hr urinary excretion for 10,079 men and women from 52 population samples in 32 countries. One of the goals of the study was to quantify the relationship between 24-hr urinary sodium (y) and estimated 24-hr urinary sodium(x) from casual urinary specimens at one point in time. The investigators presented a simple linear regression of y on x, separately for men and women. The regression equation for men was :

Y= 1.03X-7.19 with R²=0.27,n=1369

a. What does R²=0.27 mean in words?

b. What is estimated standard error of the slope of the estimate?

c. What is the 95%CI for the true slope ( beta)?