Watching paint dry: In tests designed to measure the effect of the concentration (in percent) of a certain additive on the drying time (in hours)

of paint, the following data were obtained.

a. Compute the least-squares regression line for predicting drying time (y)
from concentration (x).

b. Construct a 95% confidence interval for the slope.

c. Test H0: β1 = 0 versus H1: β1

Can you conclude that concentration is useful in predicting drying time? Use the α = 0.05 level of significance.

Concentration of Additive Drying Time 4.0 8.7 4.2 8.8 4.4 8.3 4.6 8.7 4.8 8.1 5.0 8.0 5.2 8.1 5.4 7.7 5.6 7.5 5.8 7.2