15.3 The file Sofia contains the data for a study on the air quality of the city of Sofia in Bulgaria. The study examined the relationship between temperature and humidity in 2018.

Source: Data extracted from https://aqicn.org/city/sofia/

a. Construct a scatter plot for temperature and humidity.

b. Fit a quadratic regression model and state the quadratic regression equation.

c. Predict the mean temperature with a humidity level of 60.

d. Perform a residual analysis on the results and determine whether the regression assumptions are valid.

e. At the 0.05 level of significance, is there a significant quadratic relationship between temperature and humidity?

f. At the 0.05 level of significance, determine whether the quadratic model is a better fit than the linear model.
g. Interpret the meaning of the coefficient of multiple determination.
h. Compute the adjusted r2.
i. What conclusions can you reach concerning the relationship between temperature and humidity?