Wanting to know if there is a linear relation among heat index, air temperature (in degrees Fahrenheit), and dew point, a researched collected the following data for various days.

(a) Find the least-squares regression equation yÌ… = b0 + b1x1 + b2x2, where x1 is air temperature, x2 is dew point, and y is the response variable, heat index.
(b) Draw residual plots to assess the adequacy of the model. What might you conclude based on the residual plots?

Dew Point Air Temp. Heat Index 90 64 93 90 68 95 94 66 99 94 70 102 96 70 105 96 76 111 99 68 107 99 72 111 100 74 114 100 80 123 93 72 103 93 78 109 97 80 118 92 82 114 95 66 100 95 82 118