A coal miner’s job is extremely hazardous and can cause serious health problems, for example, black lung disease and vibration-induced white finger. A study was conducted to examine the hearing loss...

A coal miner’s job is extremely hazardous and can cause serious health problems, for example, black lung disease and vibration-induced white finger. A study was conducted to examine the hearing loss of coal miners exposed to years of vibration and cool temperatures underground. A random sample of coal miners was selected, and the length of time on the job (x, in years) was recorded for each person. Each miner took a test in which the hearing threshold level (HTL, y, in dB) was measured. MINER

 a. Find the estimated regression line, and compute the residuals.

 b. Carefully sketch a normal probability plot of the residuals and a plot of the residuals versus the predictor variable.

c. Do these graphs provide any evidence that the simple linear regression assumptions are invalid? Justify your answer. How do you think this regression model could be improved?