Some research suggests that higher levels of carbon dioxide (CO2) increase the rate at which plants and trees grow.6 In fact, even without ideal conditions (for example, normal precipitation and...

Some research suggests that higher levels of carbon dioxide (CO2) increase the rate at which plants and trees grow.6 In fact, even without ideal conditions (for example, normal precipitation and temperature), some trees grow more in elevated levels of CO2. Suppose that, in a research study, data were collected on oak trees in northern U.S. forests. For randomly selected levels of CO2 (x, measured in parts per million, ppm), the most recent tree-ring growth ( y, in cm) was measured. The summary statistics are given below (n = 10).