Concern over the weather associated with El Nino has increased interest in the possibility that the climate on Earth is getting warmer. The most common theory relates an increase in atmospheric levels of carbon dioxide (CO2), a greenhouse gas, to increases in temperature. Here is a scatterplot showing the mean annual CO2 concentration in the atmosphere, measured in parts per million (ppm) at the top of Mauna Loa in Hawaii, and the mean annual air temperature over both land and sea across the globe, in degrees Celsius (C).

A regression predicting Mean Temperature from CO2 produces the following output table (in part).
Dependent variable: Temperature
R-squared = 33.4%
Variable .............. Coefficient
Intercept ................ 15.3066
CO2 ............................... 0.004
a) What is the correlation between CO2 and Mean Temperature?
b) Explain the meaning of R-squared in this context
c) Give the regression equation.
d) What is the meaning of the slope in this equation?
e) What is the meaning of the intercept of this equation?
f) Here is a scatterplot of the residuals vs. CO2. Does this plot show evidence of the violations of any of the assumptions of the regression model? If so, which ones?

g) CO2 levels may reach 364 ppm in the near future. What Mean Temperature does the model predict for that value?

16.800 16.725 16.650 16575.. -.. ' 16.575 16.500 t 337.5350.0 CO2 (ppm) 325.0 0.075 0.000 -0.075 325.0 337.5350.0 CO(ppm)