The following data were taken on a highway:
Speed (mph) 70 55 35 30 30 25 20 10 5
Density (vpm) 5 10 40 50 45 65 70 105 115
a. the mean for both speed and density
b. the standard deviation for both
c. find the covariance between speed and density
d. find the correlation coefficient
e. 90% of the speeds are between _______ and ________
f. Find the Z-score for all density values