=+ Consider the following monthly API and statewide crude oil index (COI) values for California during 2010−11, obtained from the California Department of Transportation.

COI API COI API 385.1 415.1 474.3 477.1 408.0 377.0 483.4 488.9 400.8 402.8 504.9 586.3 426.0 427.3 616.1 634.7 437.0 436.9 656.6 667.5 384.0 360.8 606.0 592.2 393.3 372.3 579.0 565.9 402.9 417.2 588.4 570.5 404.2 376.5 536.8 589.7 399.5 424.1 585.9 559.8 438.9 432.2 592.5 637.0 447.8 450.6 650.0 625.0